OzVMX Forum

Marque Remarks => Yamaha => Topic started by: alexbrown64 on October 11, 2014, 07:27:16 PM

Title: YZ125K Rebuild
Post by: alexbrown64 on October 11, 2014, 07:27:16 PM
Edit: Hi, well its July 2017 and photobucket decided to charge everyone 400 US just to host some pics... then they blocked all the pics on the forums.... so i am deleting photobucket... so bare with me as i download and re upload all my pics to OneDrive and then link them back here.. thanks, Alex

Hi all, well i haven't seen a lot on this forum about the 1983 YZ125K so i thought i would start a thread up.  I used to race the K back in the day and thought it was the best Yamaha i ever rode.  It just seemed to do everything right and i never had any hassles with it.  I also had the 125 F, G and J and they were woeful in comparison.  I also believe that the 125 L and N went pear shaped so the K was just the lucky one.
Below is a shot of me on my K at Noble Falls WA back in 83.
(https://2pt5ja-bn1305.files.1drv.com/y4mDxMhWgBFJopVU3mPcJHdUZvnNr6r0nWNM7Bw-wmhrXbRGJwAshjyevhpM3iS2KyQI-QhGJUlX0V6nGLeHvX3mNBCZ7vteKAefRRtY8qWYTjZ3INMjzp_7gwR65hdAfLg6fTr6zjBU9AfWiUBLN6SelUZPjaOFu689m5_-yrd1ifjogpkSKsKR0G3vX8O2_Dh_KFSwzC9z1T5NKYVEVcJnQ?width=660&height=369&cropmode=none)

Anyway, as an old fart now a few of us have taken an interest in some VMX racing and i have decided to relive my teenage years and rebuild and ride a K.  I have a website i have created with all the information i have garnered for the project so far. You can get more info from http://yz125k.weebly.com/  They are a rare beast but i found a nice one in America and it is on its way as i write. In fact i think it is in Singapore at the moment.  Below is a pick of my yellow US edition.
(https://nwtr7a-bn1305.files.1drv.com/y4mEIpTfGCYZJI2mExAOQuxOxpy9qsY920tzUR0jt5qFn_wuLaLpnkTfdFsQChDr4xwTRO4R6sfBwcoenJRPedX0XeDt0yYw0fXlm7XsGt-ehjVyAHJ7gs3-0sGbQjT9_R4TSp4ppbypXSFvwY7ogZ_N3jO18hSM4IBCYuYH3yTnOuP1WyESIaifkFNFI3WXm67g2tUZzl_hm8YOm19vSf0Mw?width=660&height=495&cropmode=none)

Its been taking ages to organize the bike and get it over so i have had plenty of time to organize the project.  The idea is to set it up as per the 1983 Yamaha Race Report that came out.  I have put a copy up on the website.  I ordered a Jemco cone pipe from Jon Easton and it arrived a while back and looks pretty good.. below is a pick of the pipe...
(https://ffcjga-bn1305.files.1drv.com/y4mhzjClG1n4oQMY8zbzXrZLAm2pRSVIh3w8dRniL15wxc1TBciCPygyBnl2pMitJutTYwjTmPq0rnfRjmJOFkhSsvhaNZsd64gYhAu92hwkgwALXf95yCAh56hQbh2dFgl1CZY_imiPaQDf6LpQRYcNvrgllSgAr5ECkh5UC7kbZtOO3RmASktzHsdxfHBuwbgMcJEgAlnpJk5RuvQNizUvA?width=660&height=495&cropmode=none)

Also on the list was the updated carby and specs as per the report.  That was hard as the specs call for a 36VM with a 6f34 jet needle.  These are impossible to find so i found a bloke that measured his NOS one and i made a spread sheet to calculate a suitable alternative based on available needle jets, jet needles, profiles and the area created between the two jets at 10mm increments.  I believe i found a suitable alternative in a 6f4 using an alternative needle jet to go with it.  Below is what the Race Report calls for and below that is what i have found.
(https://nwq2ea-bn1305.files.1drv.com/y4mHD21P4fd8C9WJ0jZSQ77Ms_Y2OOw8r8mlfbIuXTgd_e5CPIMoJRCDcSilzRdWQsLl9_7uIbvyefPsyFHf21Iah9HcrfCMR9d8ExUjEfY9k1HOJ91lAidjhOFaG5axB7GDRw5RKeISEMlMclSNwChZl6gqotveKDtGv6mbJXi_Ql9OZ9Jzb8qAiHWBQnRcJX1h1zMDV3EHXWi8ADdDG4yWQ?width=660&height=586&cropmode=none)

(https://ffdnxa-bn1305.files.1drv.com/y4mMCX3MwjO3xhzFdR4km_L5yhPIsC4bLQPAJ1MpysSHnKrAtHrMoFgaMWQ6yf9U0llXjsHD0Cpdt-goFOPGUnZKIuQv1UnJMm9Ws_CMy2SksOfpAeG8oyQHLU3y1wkb70mLl9AYsZFNiY_wMu42_M3Rt2i5kCqRxvSOpHl8pATR5GDdJ-p7e_QHOHyaNqsIkzYhDJb6sznoA94VxgBDifLtg?width=660&height=588&cropmode=none)

I believe that a 30 year old ignition is prone to failure so i did some research and went with a PVL digital ignition... below
(https://ctc5jg-bn1305.files.1drv.com/y4m0AkTSJu0D1YkSBQ4Ixlq-TL-AecOcfhFRwOwQSzt2Zrz2cQ1a9BSgcgw8BdlQlFDVuSHqGu-rfHYHgjULio6m6AU8mAhbWEwNHYppLWFKAI55REw4kcOcZhZNldyvS1EAoI9L42feDvmH13l5R4B2UazAPuYcpX2wrgC9i1PUHvjuxeRRPIWUNrMZqo5hgOMrLIO0wjHIttkEY13EHfgvw?width=500&height=375&cropmode=none)

I then made a dial indicator for it so that i can set the timing when i eventually fit it....
(https://4durja-bn1305.files.1drv.com/y4mqGgWc5cmqDsrG-Q1Ley1sspQI_qCV_Gjzr4jno3J890uu_CqpL_4Yr6lQ76EC8Ycnyj6YFpCyTI-JTAPupx3LB_yUL2w88P0e36_DoI8xjvD9te5mIEWHG7A2M2PbB9uSVrOv41QndcykddCLHn0jr2vLgMgvs1FwcdPwJdowi8eJYRPIR7gcuiG9vkEzw4KkzLVtsQpZcR1zltwYGJmWg?width=442&height=660&cropmode=none)

OK... i have more to write but i will put that up next.....

Title: Re: YZ125K Rebuild
Post by: mudguard on October 11, 2014, 07:51:08 PM
I'm liken your bike Alex 8) Don't give away too many hot up tips Alex. Just may give someone else the edge. Lol  ;)
Title: Re: YZ125K Rebuild
Post by: 80-85 husky on October 11, 2014, 07:52:30 PM
I hope the bike shows up!
Title: Re: YZ125K Rebuild
Post by: alexbrown64 on October 11, 2014, 08:06:25 PM
I also wanted to sort out the cooling system so that i would not have any future hassles.  I read some reviews on the ally rads that are made by Winner and GPI and ordered a set of GPI ones.  My first mistake was to assume that the picture of YZ125K rads on Partzilla.com were correct.  In fact, they show rads for the L and N.  Below is a pic of the rads i received and an original set i purchased on ebay.
(https://nwrsyq-bn1305.files.1drv.com/y4mBSh53l9VRo5Yk084EpHelTqdJXNeFQQkaBI1q5AZE5tBnJykARlgiFfHEg32VxnD7Xwu1i2rm1Ac5pAncCBcTLKm4bVaYj3Eg5RP_LZIwHPPvbroXJ2RJU_oRy6bH26BeawIvBULebhzPRhaOEFyUrhYzYEhRamthI2CyFxfh8oaENkASPGSIa_Hvv0_gxXlRchcHWgTnlNR0QLPv8R_Pg?width=660&height=495&cropmode=none)

I contacted GPI and they said no worries, just send us the rads back with the originals and we will reverse engineer them and send you back a set of custom made ones together with yellow silicon hoses.  I have sent everything to them and the last response was that they have drawn them up. 

I have also been on the AllBalls website and ordered all the bearing kits for the bike.  You can just about get everything including steering stem, linkages, wheels and swingarm.

Partzilla.com was used to order new cables, brake pads, engine and transmission seals and bearings, conrod and other bits and pieces.

As for suspension, i found a bloke that raced a YZ125K in the vet class in the states and he told me to contact Matt Wiley at Race Tech USA.  Matt was kind enough to send through all the details of the suspension work that was done.  This is supposed to give the bike a really nice plush ride.  Below are some of the specs but the website has full details and prices.  When i am ready, i will send the suspension off to Terry Hayes at Shock Treatment as he is the Australian Race Tech guy.  Matt gave Terry my details and Terry contacted me and is glad to help out when i get the bike.

1983 YAMAHA YZ125K SHOCK RIDER 175lbs & WANTS PLUSH RIDE

VINTAGE SHOCK REBUILD

SMGV 4616S
SK GOLD VALVE 4631 SHOP
KIT
SPSC B5747
SPRING SIZING COLLAR- 23
EACH
SRSP 672750
RT SHK SPR 66.9x64x267 5.0kg
KIT
SYSH 4614
SEAL HEAD 46x14x19 no t/o YAM
EACH
SSBO 144439
B/O BUMP 14x44x39L SHOWA
EACH
US1 PT
US-1 LIGHT (pt) REBUILD
PINT
LS12

83 YZ125 FORKS
 
FRSP 305543
RT FRK SPR 30x500mm .43kg
PAIR set @ 5mm Preload
 
FEGV 3801 Gold Valves
EMU VALVE SPRING 40 lb BLUE @ 3 turns
4 Bleeds Valve Plate
15wt Fork Oil @ 130mm Oil Level

There are a few guys on this forum that ride the K and have helped out with advice after seeing my website.  If anyone else has any info, pics or advice to offer it would be great and hopefully we can all work together to get some great K's racing out there.

Cheers,
Alex
Title: Re: YZ125K Rebuild
Post by: alexbrown64 on October 11, 2014, 08:18:53 PM
Don't worry Wayne, i dont think there is much out there that can touch your K.  Husky, i hope the bike turns up too.  I have the shipping docs so hopefully it should be OK.

Another thing i forgot to mention is the engine.  A full rebuild is in order and i have a bunch of parts like bearings, seals, rod, gaskets, clutch etc.  When i finally get the bike, the cylinder will need to be inspected and then sent to Eric Gorr to get bored, ported and a new piston matched up. 

Cheers,
Alex
Title: Re: YZ125K Rebuild
Post by: alexbrown64 on November 07, 2014, 01:14:40 AM
Well, bike finally arrived in Fremantle.  Now i have a problem.  I dont have an import permit.  The website says you dont need an import permit for an offroad bike.  However, you have to apply for the exemption to not have a permit.  To not have a permit is a 10 page document with 9 attachments, fifty dollars and a 3 week wait... while my bike accrues storage fees at Main Freights yard. 
Wish i had looked into it more but the penny didnt drop... now i have to wait for my permit which authorizes me not to have a permit.
Bureaucracy in Australia is mental...
Title: Re: YZ125K Rebuild
Post by: Richo52 on November 07, 2014, 09:44:26 AM
Great looking bike Alex.I get any bikes I buy from the states partially stripped and bring them in as parts.....it avoids the problem you now face.Good luck with it all.Catch up some time Richo .
Title: Re: YZ125K Rebuild
Post by: 80-85 husky on November 07, 2014, 08:07:35 PM
Guys... since the unruly mob showed up at Botany bay, the greatest lurk to all involved is screwing punters to get stuff into the country...allways has been allways will.
Title: Re: YZ125K Rebuild
Post by: alexbrown64 on November 16, 2014, 11:56:06 PM
Well, bike is in Freo.  Now, major problem.  When i read the Gov Dept web site originally, it says you dont need an import permit for a dirt bike as it will never be registered.  I left it at that.....big mistake.  You still have to apply to get permission to not have a permit.  It is still $50 and 10 pages, plus 9 attachments and a 20 day wait.... except they dont give you a permit... they just give you a permit to say you dont need a permit.  Now my bike is sitting in storage accruing fees....

Anyway, sun will be up tomorrow and im still breathing so its all good..

Cheers,
Alex
Title: Re: YZ125K Rebuild
Post by: alexbrown64 on December 08, 2014, 12:43:35 AM
Well, "they" finally let me have the bike after extorting a fortune out of me.  I was expecting a fee to get the forklift to put it on my trailer.
Anyway, bike was filthy, decals bubbling off and at close inspection the old girl is a piece of shit.
Below is a pic of me finally getting the old girl home after a long trip from New Jersey.

(https://4dsqug-bn1305.files.1drv.com/y4murQjyyK6uiYkhwqDXKDzeWt1ohAagN87C43Jtd1NHIYEv0_7BlKqMuv3liWkeL5548ZCP2YCXGVM22X2W8ALiVcz0znr9ISvR_yq11R93lLUbavE9J8YkhGWURgyRLC_zepmZe5wKYjONP807r-UWFvhvff1HnU4QCaMipyb-erDNHsbSbho835Aww0phfwNM9QmJUobHkXOHWtKsaOr2g?width=660&height=495&cropmode=none)

Ive decided to build the bike after Ron Lecheins 1983 works OW125. Of course i cant have the rotary engine but i will theme it that way.
I special ordered some white rad shrouds from DC.  Also ordered white side plates.  The motor will be blasted and i will try to match the OW125 case colour. 

First things first... i wanted to check it all out and get it running.... Put some oil in the tranny, some juice in the tank, check the airfilter, check spark, 30 kicks later and she is running.  Sounds a bit rough but it hasnt run in a while...

Before i tear it down i want to test it with the new carb, pipe and ignition.  First i put the Jemco pipe on and run it... sounds good.  Next i play with the new VM36.  This bit took 2 day as it kept flooding.  I rang Tom at MikuniOz and he said dont touch the float...its factory set.  I tried everything but it kept flooding.  I went from 18mm to 22mm float height and it ran like a beauty...pic below
(https://ctdvdw-bn1305.files.1drv.com/y4mUH8k9UOUXH206GsinEOuF3UswFgxNe_NYvUhK_J1qSRfttmCvhRlJrEo_OmZPNjUOoV0i2Nq8GwPGdRk0S6yFZl_OG-b-Xh9w44o_GOcI1qbEQmE8bk6vESJlsodXGP2sbp0Gp0YfijYZA1ttRGOBKU22eHZA33xWk8ErL3VFwTJ51Ui1MjZr7xGeJyfTA8cSyCiKoeFWHOw3uMAAN55Lg?width=660&height=495&cropmode=none)

Power valve and comp test.  Power valve lined up well and a compression test was around 130 psi.  Later during the tear down i revealed a new 2mm oversize piston in a freshly honed bore. 

(https://ctcdpq-bn1305.files.1drv.com/y4mF4zjaWDRdgKl95vZ-Vpi_PnmPPyONFcIkflXJFdNxsq-3QLdkwcxUqxPlWXTk3VnOCoMp6uJlffcfMYWoEEb74GSaEySwa8BHOSue3cdFsNayj76ybs-SLVn4DV4dOhMD0IDc4Y5WEm48dpJyY9LFQv09eRwI7xP25T9IhnuP7eey3e7J8Q881RuUN01DgctSEN-IFuVpPoUMqSlHFq-4g?width=660&height=495&cropmode=none)

(https://bsli1a-bn1305.files.1drv.com/y4mBOyVSKFcHM5d0-Ck1Yko024fPOomzUte989UrWmPZt7Ds0fZwIuh3zyKEfuUSwkaPyOMnLBM7IyRjQCjC8919LgNahs_KPouRj52oJpQlt9aoPrv5-FNkc6124hpNu8G-zrWce2Ms9hQPNq9XDo9jmQ840TgRnLq857k8-0SJCvMG7AQL_Z3zCeM2VlmnrKDYvlDxJp68Tmo8gTY_aHc9g?width=660&height=495&cropmode=none)

Next up was the new PVL digital ignition.... I ripped all the old crap off and fitted the adapter plate.  It should be locktited in.

(https://003yjw-bn1305.files.1drv.com/y4mTqqQEpsJjOraeja2Ijf1Fpe824Gvi-DXCEOzsmX7b0YnkwdF6GYEI9o5kb3X0IhqG85pahR8i7_NatUtVQVehc7p8WyfEtL2f_IJQwBCzt9iK-GVzEQTwgw6LIRIFvRuJmjTzkH5Rj1XJiyKIcfpHgixTkkCzgbpadMBcWEfYJaiM__9lmy8NxyRfH0_-GwE_dClWxDjZTZwIB8amNrKGw?width=660&height=495&cropmode=none)

Put the stator in next.  Just fit it so that you have a bit of play on each side of the attaching bolt so that you can slide it from side to side.
(https://pkuqrw-bn1305.files.1drv.com/y4m9nsg5QU8tnV5D_Bua1tg2HdirmnMID798loW8dNHjOpAF2I2D2wzdRX4X9uBiKTeMS29gacf21dUVZ6OUmaknmgVqbz7mx1RPAxpTGDxurVbLez4RESLGGhM8RGwuW97OLAcpmRJ8ydP3es7y3HxYZsZn4fOv8RblnjeF3xQAEAiAvlrCvdapwS1B_Nb7be3Ok68Y-f7YbJOSSkm7kgXsw?width=660&height=495&cropmode=none)

Next, you want to put a dial gauge in the head and zero it in at top dead centre.  The turn the crank anti clockwise so that the gauge reads 1.2mm BTDC

(https://pyci0w-bn1305.files.1drv.com/y4m0Hy0OakypwtcwR-F8klOkSdSb1mhVYspXtClagZwmfiSMeE3_00ToHF5JrFuyo7hKDx1HiyWZ3Y64K5yQ5-1kO8GnilByVhtss0lJhlFlsF8wsy7Vkafe4GVTnw4zTsa_laK9IvfuZQDCNmc5IAzEe1noo54FBtlCu27S6s-MKWERy4lkzP10IjMY8yg5by3pjTtIutAatlDZsljToZcPA?width=660&height=495&cropmode=none)

Now you can put your rotor in.  Leave the green tape on the rotor for now and align the mark on the stator next to the clockwise arrow with the mark on the rotor and fit it up.  If it all fits well, remove the green tape.  There should be a tiny gap between the rotor and stator.

You have just done your timing.  Now just fit up the PVL coil where the old Yamaha coil went... its a direct fit.  Make sure its ground well.  I put the new CDI where the old CDI went by just bending the tab a bit.  I will make a stiffening plate for it later.  The wiring is simple... There is a harness to plug in and a few black ground wires to the frame from the CDI and Coil.  Your kill switch has 2 wires...1 to ground and the other to the CDI red wire.  There are also 2 blue wires that plug together.

(https://003kna-bn1305.files.1drv.com/y4mJu4F6zpvNQEONAY9Ea-3NQtyUyPCrDqYALaXMTVSRFMjFSJZY8c-JvGM7k2zJkyEYZOcbRI6LdGfFdToFJaghPvOg49W2dKPsMJOQYXNbJLtw_8mhdQ9vDTa_5fWA7022bVK4wmSMnxVtDyLRy_gh48gFjBTlmVsZ18BM1PX_bR0wze-8ppZZVcNwMTQuPg386Dki61GwSkvx-lJLPwYHA?width=660&height=495&cropmode=none)

After i fitted it all up i checked for spark... bit fat blue sucker.  The next day i went to start it.  6 month old premix and second kick it bursts into life and runs like a dream.  I took it for a rap up the road and its like a buzz saw.  Go's through the gears well.

Once i knew i had all the systems up and running, it was time to tear it all back down ready for a rebuild....
Only took a few hours to get it looking like this.....

(https://bskzmg-bn1305.files.1drv.com/y4mrKvG0BUTEp1geNAg647e_pNH8GIpNhPWC6WmiWVsimDBkdIuQsPyIFBcvsyfagasalS_gS-Q3elNKBVjr756cx3I1Xea54ALAilvGWYVdQPrVw0VmRtqnqVTb75Hob0b_2rGcQ6lJOvJ-0q2Oy-PG_t5r9PlGp2_PQ7n6aN33ybJCM0ZAX6xCmxQbonbVSMkA-ehGF8czGyhFCOnA-nHRQ?width=660&height=495&cropmode=none)

And then a few more to split the cases..

(https://001q1a-bn1305.files.1drv.com/y4msNqvqoLkgN6WCwSUpfz2l6I8FOzEl_slJEute3zvO9NjZuME1Zede0rZ4XwJbGU2WjGGE00ysZrhbjhYvoVpYLFWzrwMrUFZhxNgcopKLZiN0b65QEJUqGD9u_XCcxcfFkSfEj0BiMf2tjQUyx9iuLhFyuvETnj5YfUBONSJfN0-WhFcjW5XbD6GIBTDdK1PWSGqaHz4R7G3W1gAjU_wSw?width=660&height=495&cropmode=none)

And finally, the suspension needed tearing apart and cleaning ready for Race Tech....
(https://4dt1ow-bn1305.files.1drv.com/y4mXqcSyYnRrPkibEFvJAxVjehz735OD3HzNy_DV6xSAUsBhXo6d1ojQIKO7GGDVkY5QJzfIm5emhjtCi5XbVyL-3aZ_hHZj0aItONiL-O3_o69M_EvPPIbmOMxdjWk8qMNWAMBcTzLdsf3Ngz48pqyJTAXqFtGwx-LEbSOcTsyUeuPYpzAw3Rh5-lNJi1RaDbfhlYJPFKOfahkygtPioTQUw?width=660&height=495&cropmode=none)

I think the forks were filled with mud.  The rear shock clicker just turns and doesnt click... not sure if that is going to be a problem...

Waiting on some emails from Eric Gorr regarding cylinder sleeves and porting and Terry Hayes at Shock Treatment regarding Race Tech emulators and gold valves.

Well, thats it for now... frame needs some welding and then its off to get blasted and powder coated.  Crank will go to get new rod..

All hardware is in a bucket and is going to get some acid treatment to remove the zinc then they are off to the zinc coaters...

I think its time to concentrate on Christmas and forget bikes for a while.....

Cheers,
Alex

Title: Re: YZ125K Rebuild
Post by: Tomas on December 08, 2014, 01:18:56 AM
Great looking bike Alex. Only noticed that the crankcase looks a bit rough. Like the pictures and all the details. Good luck with rebuild.
Title: Re: YZ125K Rebuild
Post by: Simo63 on December 08, 2014, 09:09:40 AM
As usual, love your work Alex.  Having imported a few bilkes, cars and boats from the USA before, I was well aware of the need to an import approval.  I just hope the holding charges didn't break your bank.  I know of people that have imported cars without one and the costs have been astronomical .. so much so it was easier to ship the car to NZ whilst they sorted out the paperwork.

My question is, looking at your first picture, where is was taken etc, this looks like an ex East Coast Vintage bike.  Is that who you purchased it through?

Title: Re: YZ125K Rebuild
Post by: alexbrown64 on December 08, 2014, 10:14:01 AM
Hey Tomas, up close the whole bike is a bit rough. Certainly got used in its 31 years.  Kick start looked like a pretzel and everything was either cracked or broken.  But she is a runner and thats the model i was after.  Simo, it is from East Coast Vintage MX but only after i found it on Craigslist and asked him to purchase it and get it shipped to me in Oz.  Yes, ended up costing me a fortune but i will put that behind me as a lesson learnt and move forward with getting the old girl race ready. I have a an endless supply of parts coming now.... kickstart, airbox, stator cover etc.. Im not sure what happened with some of the parts i ordered from Partzilla.  I never checked them and have had them stashed in a box for months.  Finally got them out and i have a Polaris front sprocket, YZ250 rear sprocket, YZ125H clutch plates and YZ80 Boysen reeds. (the 100 or so odd other parts are ok) I have already swapped the rear sprocket for some Renthal gold bars but either i was pissed when i was ordering or they have a buggy system or someone that works there that doesnt give a shit.

Cheers,
Alex
Title: Re: YZ125K Rebuild
Post by: bishboy on December 09, 2014, 05:57:32 PM
Here's a 250 if you want a pair, I'd go for this if I didn't have the mighty KX  ;D

http://www.gumtree.com.au/s-ad/cedar-grove/motorcycles/vmx-1983-yz250-k/106330108 (http://www.gumtree.com.au/s-ad/cedar-grove/motorcycles/vmx-1983-yz250-k/106330108)3
Title: Re: YZ125K Rebuild
Post by: alexbrown64 on December 09, 2014, 11:38:19 PM
I think its gone Bish, as Gumtree says add no longer available.  To be truthful, i rode the 250K back in 83 at Bunbury and didnt like it.  In the thick sand and giant whoops, i found my 125 to be much easier to ride and at my age now i need easy :-)
Title: Re: YZ125K Rebuild
Post by: alexbrown64 on December 15, 2014, 01:50:14 PM
Thanks Tony.. i use photobucket to host the pics.. its a pain.  Heard your project is coming along too.  Glen is having some major dramas with his frame.  I was lucky, i got my dad to tig my frame up and i should be able to pick it up from South Side powder coaters this week.  The local guy was too dear.  Southside is blasting, undercoating and powdercoating in gloss black for $140.

Just had a setback with the monoshock.  Grant at Shock Treatment rang and said the shock is knackered.  They were not hard anodized internally and wear out.  My shock was blown when i got the bike so probably worn out (like the rest of the bike) for years.

I have just purchased three, yes three YZ125K monoshocks on Ebay.  All known working ones with damping.  I will give all three to Shock Treatment in the hope that they can make one fully rebuilt good one.  If they can make a good one up, they will hard anodize it.  Then they will send me back the rebuilt shock with gold valves etc, and the old shocks for spare parts plus my fork kit with emulators and new springs etc...
Title: Re: YZ125K Rebuild
Post by: alexbrown64 on December 18, 2014, 09:00:02 PM
Quick update:  Just got the frame back today.  Looks great in powder coat gloss black.  Also got all the hardware back in fresh zinc electroplating.  Now i am ready to start bolting a few bits back on.  Pics soon..
Cheers,
Alex
Title: Re: YZ125K Rebuild
Post by: alexbrown64 on December 22, 2014, 12:09:18 AM
Started the rebuild and first up was fitting the new steering stem bearings.  I froze a few things here and heated some other things there then bang, whack and it all went back together.
 
The swingarm took some time.  The anodizing was all scratched up, so i made a caustic bath and soaked it for a few minutes to get all the anodizing off.  Then a bit of sanding and a nice buff for a polished look.  The allballsracing swingarm and linkage bearing kits were fantastic.  All sorts of bearings, seals, bushes and bits and pieces and it all fitted up nicely.  I just whacked out all the old rusted and knackered seals, bushes and bearings.  Then i gave everything a light hone.  I pressed all the needle roller bearings back in using a 4" G clamp, large washer and various sockets. Everything was then fitted up using the newly zinc coated bolts and plenty of grease.

The tank was sanded back and Wicked Tough decals applied.  They are great decals and hopefully wont bubble off as i think they have worked out how to keep them on.  Then some Plastic Renew was applied to get a nice shine on the tank.

Southside Powdercoaters did a great job on the frame and it has come up super tough and like new.

(https://pkvgma-bn1305.files.1drv.com/y4mBvVlKg7PddPHZCDD-6FRYxISHVFn98ctrHtHVyoXFUhRUO-9GakKnv_pSfzcYwTxvu6sM0sVNfROFhdBGTMY8pK1mElkDuig2A-bXh5_T898Mv9yfh4WUqT1G5QL_DMSmjp587A6mVuHGaRYutScb7fHAad4zv1F9s6YesK95yvsX8dJxOAjcJdEdq5Xl_pOUSy5MD_3eoB3ZkjH5gl5pg?width=660&height=495&cropmode=none)

Cheers,
Alex
Title: Re: YZ125K Rebuild
Post by: alexbrown64 on December 23, 2014, 12:36:37 PM
DC plastics arrived and they are not too bad.  I had the shrouds custom done in white.  Bolting up was a pretty easy process.  Cutting the slots to look similar the the Lechien OW125 took a bit more time and then taping them up and painting the number plate backgrounds.  Front and back guards were also fitted after a sand and buff with Plastic Renew.  I took a trip to Masters and they have 8.8 bolt kits with about 150 various size bolts from 5mm to 8mm for $25.  The only problem is that they have a dichromate yellow gold coating.  I soaked them for 30 seconds in vinegar and that removes the gold while retaining the zinc underneath.
Below is a pic of how the OW125 tribute bike is coming along.....

(https://2prz7q-bn1305.files.1drv.com/y4muVmwGiYgbN-DVZcIAsDWCDaPe_hnk_BsKrg4G_jpK-kT7BpxGWgfX_zRMgAO-CuPX8Bg9FcFeH6e3kRw0Wyc6u44GCqS8cBMR0uiYQthXdtXqYreOZnGPST0zw7jjbuk5S-F0l33pIu9mTLuWRuciTgHo8U8AI0GjcrQXvBjDYsdAUwfmPmUZcsh7Jye0Tpi83oZdhAE2XX84jmlNfNa9A?width=660&height=495&cropmode=none)


Cheers,
Alex
Title: Re: YZ125K Rebuild
Post by: Rossvickicampbell on December 23, 2014, 02:02:12 PM
Alex - are you going to cut the side panels short?
Title: Re: YZ125K Rebuild
Post by: alexbrown64 on December 23, 2014, 07:38:33 PM
Hmm... i have looked into cutting them shorter but the design doesn't really allow it as there are thicker tabs at the front to keep it all nicely tight under the seat.  I cant make a replica bike but i have a theme going with a bit of poetic license. 

I had to repaint the number plates again today.  I rushed it the first time and put the paint on too thick.  It all cracked.  I used some paint stripper and washed it all off, sanded, cleaned and taped up then used some plastic adhesion paint followed by some satin black.  OK now.  I may get some nice sheets of thick vinyl satin black decal sheet later.  I also fitted the PVL coil and CDI and put the front fork tubes in to trial fit the new front number plate.
Title: Re: YZ125K Rebuild
Post by: alexbrown64 on December 28, 2014, 05:05:17 PM
Ive decided to log what bearings and seals go where in the K and also what size or type they are and what the Yamaha part numbers are.  Below are 5 pics of the cases with most of the information needed to help rebuild the engine on the K.

(https://bslpvq-bn1305.files.1drv.com/y4mn7CY0YWf8NFiL7PnRrtED4uagyHGcS3uGULRQ40J4roU-f4YwsGiVu3u_CIy6eTHqVo9KeXVcH1yC7Kb5vp3Za8d5RK7IDjAeWP4Q1iYldHTPoHaHjukhGkbD3ZwYeZaKuYXlrzfcs7kt8nsBE6uZGnMIVebEfv4ExCeQZMLRD1lOjaqPAnfcBeQs2yzw9AbcT1J2VZz7Vq2ZxZvOsw_-Q?width=660&height=370&cropmode=none)

(https://bsjjsq-bn1305.files.1drv.com/y4mB3uV7uHm8TbZg6W21l8cPtm1bxHVIxX6tW4pTO_NK8rTXmWjvG_urvNPznF71ZZsfgFUFmxzerGkaPeqBuBHYrQ79_GHs5AiZ0xMfX5Hsejm7owiNA_VjsgZkMOnZ_SLNp_OBmGCFuvaZhUW15Rb9DLoxsJi55Bl4kl8J4iUcRb3V-14k7WWHU29uqoDLBATsBMhsMiuNS7iiIfmo3-X1w?width=660&height=370&cropmode=none)

(https://ffakjq-bn1305.files.1drv.com/y4mkOdqm_0z8sNNW70bIfo4t-wXLLYd6WLZi3uMYhyuB9yfHWFkvkp2r0o_oREfvb8qOcoJ2jAuzndFIPFOQxayh3aHPdXBE-0Zfu1FzlFHRWwqiktgRwghw0bfYzal_vXSQkwrWoeCQ4_pQx1vMRs7gItNyj4NOJoHOk6DlUAXtLfwt2J7HiFw95XvQ_CqhXpbG5jWg-o4Y64JKy5a7q2-Cg?width=660&height=495&cropmode=none)

(https://ffcc0q-bn1305.files.1drv.com/y4mXrLjTAWtOUfc0SAFglbsmDpSYAlDqdB3dDc0a5qIa8K-mIbRnLuhcv-Z1lBsp-8QrUZLr3UpZj9JiVYh79BkxeQ-rB59tvVbeNU6nuSZAQyIpDMB3jn-HseD9ger1O1epxZklUDT4AGXzbLyKS_CralBAP23MJ5EN0Tpez5psLctBRBxTFOInRWAoHHnmxN1OpUCmMXF0GfhJU32cGrXqg?width=660&height=370&cropmode=none)

(https://pktfva-bn1305.files.1drv.com/y4mURH_X_Sp-ur2VhmesNDgnv7Ul42vboY-u419NfVF4ZifxW8k7Xt-lXNW7ra6073vocTHyk9ZbcB3qVmRP65HB0cZTWxdLt-odmfPXVxvhUMyQvPM1VazKLFu-poygEew1YRoJSr47lnr8RjcBIM9rlVMvo5pgYM_q5ejX1g2HgyaTTr3QECvcQbAADYeOC9LDdM644N8swtJRB_nM4_Y-w?width=660&height=495&cropmode=none)



On a side note, a used cylinder, cylinder head and powervalve was purchased in the US.  This is being sent postage free to Forward Motion for Eric Gorr to resleeve and fit Wossner standard piston, port, machine the head and powervalve to suit and bead blast. Will be like an entire new top end but with the Gorr magic.

Cheers,
Alex
Title: Re: YZ125K Rebuild
Post by: alexbrown64 on December 29, 2014, 02:10:32 PM
Righto, some updates.  The cases in the picks with the bearing and seal descriptions are not mine.  I just used some photos from Ebay and then added all the text boxes and data.  My cases are rooted.  The clutch arm housing has been worn away and i have a major problem with the main bearings not being an interference fit.  That is a another thread.  I found another set of 83 cases on Ebay and Shane, the owner, trial fitted the mains.  He said they would not go in without heat etc.. so hopefully they are a good set.  The pics looked good.  Anyway, $110 including delivery so that is pretty good. He has popped them in the post already.
The cylinder is on the way to get resleeved.
The rear shocks, airbox, kickstart and a bunch of other stuff is in Hong Kong and should be here soon.  Then the shocks have to go to Shock Treatment.
Renthal bars ordered locally from Dave Langston.  He is also pricing up and looking at availability of Gold Excel Takasago rims.
Crank is in Witch Cycles.. should be ready in a few days.

Even though its Christmas/New year, things are moving.  My neighbor just popped round.  He is trying to weld up a 1989 YZ250 frame.  Having a bit of bother with it but hopefully he can get his frame off to the powder coaters soon.

Have a good New Year,
Cheers,
Alex


These are the actual cases i have purchased...
 (https://pybnvw-bn1305.files.1drv.com/y4mUglTcubXjKHFuDb1yCgBBCLhLqvDrEwf0bLU21zeTGbk3ROEL0kDBLqVlsc_XBgSVAxcJPpvWakN9QrIVZ3V7SCDNuU-Oz2_xC_9W8-Xdk-O1wZhcDbfvjNaJCnil7bSA_p92JwFttQpMmbsDjZQ4O7xUorBJPMfqrvkkV5EHaTxtwZyiXd3-j5OtiFfFRgIAJRNLGnFybk0jmImQieToQ?width=660&height=495&cropmode=none)
Title: Re: YZ125K Rebuild
Post by: alexbrown64 on December 29, 2014, 04:20:14 PM
Well, that was going to be it for the arvo as im taking the kids to archery and then off to the grandparents.. however, my decals arrived from the states.  In keeping with the Lechien tribute OW125 spirit, i made up some decals the same as on his rear fender.  I used http://www.stickeryou.com/2 to create the logos from ones i downloaded from the net.  I then edited them and made a few A4 sheets worth.  I also have some other decals i designed and added to the A4 decal sheets.  You can do most of the editing and stuff on their website.  Its not a bad website to remember as i created my custom decals, had them printed on vinyl to two A4 sheets and they only took 2 days to make them and posted them fast to Oz.  All up cost was only $25 bucks.
Pic below of them on the bike.
Cheers,
Alex

(https://4dtgaq-bn1305.files.1drv.com/y4mLwmi6pDphjdZMyQV4tSXs-1TMuOev_RzcgaUyQ1BvBfyEH4mwp3wjBHdZcgQq3-YBehvUqD6TB3iGGvChjOG7LF_U1-UQu5ld_BlRPCB5MZeZKRT7PK4lBIfNEAX_WELZw6wh_NiNFeYHmYwjsBfZsf2-vMDxwZ6r95Lec1rCIVkMGdwCSzZt7nUXtEkJ6rZ1dZZg7s_Sz7M7CsMkVhqpw?width=660&height=495&cropmode=none)
Title: Re: YZ125K Rebuild
Post by: BJJ on January 02, 2015, 08:48:10 PM
Whata great project,  looks awesome
Title: Re: YZ125K Rebuild
Post by: alexbrown64 on January 08, 2015, 05:16:12 PM
Another quick update.
Trial fitting things up. Cone pipe and muffler fitted.  Will have to make a few small adjustments to the plastics as they touch the muffler.  I fitted the brake stay arm and used 2 sealed bearings instead of the spherical bearing and 2 seals that were originally in the front of the arm.
Wide footpegs fitted.
Cases should be here by the end of the week... crank is ready to be picked up from shop.
Cheers,
Alex
(https://nwqh1g-bn1305.files.1drv.com/y4mP8J-C57NRrJKZGLYJ1hLc2XcjLY2sRO1qukhq8bgQU-VjWSnuGSBQBmWIzlik_x4tqdxbxt1cj2m_2H_Aiqr8BBT5Y4lt3S7YUFSCK1e_Skxzrwn-tijoWvFF_RuqKWz4R15SlkPF6TKZ_zdQIZoogrAHPIbKCS1VTOmupxvk4SY4Dh-Pqy1eULtUlTDsavOpXG7y-koxDVBaiHrZkmAlw?width=660&height=495&cropmode=none)
Title: Re: YZ125K Rebuild
Post by: 80-85 husky on January 09, 2015, 09:02:05 AM
spherical bearings are usually utilised to account for radial forces......have I missed something? will the std ones survive?
Title: Re: YZ125K Rebuild
Post by: alexbrown64 on January 10, 2015, 05:18:40 PM
I hope so.  I read somewhere that the brake stays on different brands can come with spherical bearings, bushes or roller bearings.  It only goes up and down a few degrees and i have put 2 heavy duty sealed bearings in there.
Picked up the crank yesterday.  Witch Cycles did a good job on rebuilding it with the rod kit i gave them.  Just waiting on the cases... should be here soon.
Ordered the new rims as well form Dave Langston at The Moto Shop.  Gold Excel Tagasako. 
Title: Re: YZ125K Rebuild
Post by: Woody on January 10, 2015, 08:43:52 PM
top class restos there Alex, I'm luvin the brake stay rod. Did you fabricate it yourself?
cheers
Title: Re: YZ125K Rebuild
Post by: 80-85 husky on January 11, 2015, 08:56:07 AM
a few degrees wont matter eh. she'll be fime
Title: Re: YZ125K Rebuild
Post by: alexbrown64 on January 11, 2015, 01:08:34 PM
Should be fine Husky.  Thats why i wouldnt mind knowing what sort of arrangement other members have.  The 85-89 Honda CR's have the same brake arm and all they run are two collared bushes (10) and two seals (26). 
Cheers,
Alex
(https://4dtujw-bn1305.files.1drv.com/y4mHrqXhMZx53IGeGkrO-K8VBSXeZvxM8B2Gywm6P6XLWKLjyO8Qzmze8-7fDqRFeG1p9Sh0NZpLdwf91VE7_mZfIgiQ9kegA0zmL5N_OR7IHda1M3U2v-dye13ZNpTWe-cWgbZsr63HaMM0usBuTZ7szEfZ0uT5F6-v84X5D0UM0IQd0d15OaD20paeFA8tcylFYNI2ogPW3hLPtYtXr2s2g?width=660&height=336&cropmode=none)
Title: Re: YZ125K Rebuild
Post by: alexbrown64 on January 12, 2015, 12:38:46 AM
OK, an update.  Quite a few months ago i purchased some GPI radiators for the K.  They advertized them for the K and L model.  Unfortunately, when i got them they didnt fit because the L went to the rad cap on the right side and different plumbing and that is the only ones that they made and sold (although they advertized them for both models).  GPI said no problem, just send us the rads back, together with your original ones and we will reverse engineer some.  Well, my bike was still coming from the states, so i located some cheap OEM ones and some hoses, then sent everything to GPI.  Just had an email back with the first pic.  Apparently, my new rads and hoses are in the post so heres hoping.  Below is a pic of my bike with its bent and twisted OEM rads on it and below that are the new ones that GPI have reverse engineered using some good ones i sent them.  Just hope it all fits :-)

(https://ctelya-bn1305.files.1drv.com/y4mBoZ2ohD12P-MJoPmt10UoWU3ytLt4vl8l10YXBNnDx03dtr5474F9WayKHO86hG0Rh_Sshxjnx3WCoNdy0pWqWAaB8i3w82qT7H9XnHDybabWMn3rxEjiVRdR5-Tbzukvph3n4XKDxMUcd2QoJgb2DUpERDR00npsUS23d6qhjzaJ-jkZgJLeGyip89D4yYfFZ3J7Oqnioz6dIay9iiDLg?width=660&height=495&cropmode=none)

Same should go for anyone else.  If you have some ratty rads and cant get replacements, then ask GPI to knock you up a set.
Cheers,
Alex
Title: Re: YZ125K Rebuild
Post by: 80-85 husky on January 12, 2015, 10:07:09 AM
the wr husky's just have a small collar and o rings (swing arm attached) while the cr huskys have a frame mounted torque arm with spherical bushes....I think :)
Title: Re: YZ125K Rebuild
Post by: tony27 on January 13, 2015, 08:01:52 AM
What was the OD of the bearings at the front of your torque arm, the 490 arm I fitted to my 465 & the standard 465 arm used a bearing with 22.5mm OD which isn't available. I had to shorten the arm 19mm to fit the 465 so I remade that end to take a GE12 spherical bearing which is an off the shelf item from any bearing supplier
The bike will certainly be a looker when finished & hopefully it goes as good as it will look
Title: Re: YZ125K Rebuild
Post by: alexbrown64 on January 13, 2015, 12:49:43 PM
Tony, it was 19mm.  I could get a spherical bearing but it was expensive and i would still need a seal each side to stop muck getting in and wearing it out.  I got two 19mm sealed bearings that are 6mm wide each.   They fitted perfectly.
Update: The cases arrived in the post and look good.  I removed the last 3 blind bearings with a combination of techniques including wet wadding packed into the hole to pressure the bearing out, also had to run a small weld on one to loosen it... all worked OK so now ready to blast, paint and install new bearings and seals.
Title: Re: YZ125K Rebuild
Post by: tony27 on January 13, 2015, 01:01:09 PM
I just used thick O-rings as seals, pretty sure that's how my TRP shock in the back of my trials bike is sealed & I've not had a problem with wear even with the amount of water we ride in
I found wear in the brake plate bushes & sleeve, a piece of ejector pin drilled & reamed fixed that, seals were available unlike for the brake pedal which ran steel on steel for it's pivot
Title: Re: YZ125K Rebuild
Post by: D project on January 13, 2015, 06:53:25 PM
Wouldn't having no spherical bearings affect your floating rear hub. When you apply the brakes it needs to centre itself to get good brake shoe contact in the hub?
Title: Re: YZ125K Rebuild
Post by: alexbrown64 on January 13, 2015, 09:42:56 PM
See pic above.  The Honda does not use spherical bearings.  Also, the front of the brake stay (where the bearings/bushes/seals go) squeezes between two plates in the frame, to which it gets bolted to.  There is no where for the rod to move except up and down, which is what my brake stay does smoothly.  D Project, you are correct that its important to keep the floating free hub "free".  I think a pic is needed so have taken one of the YZ125K brake stay arm and how it is bolted between the two plates on the frame.
(https://onkikg-bn1305.files.1drv.com/y4mpspiggHJW8a1WN03U-ylaKy7dELU_zMcIHGOskgHD82P5eIFBcxkqMbHc-pH7GxRh99Jxni91isPA4C2YsrmyVpcgmPvJid6faVuln69P7taF3bzZi4rAgCwBUUJwE5WMdXzRr0m05n_DYKBWTLWldQWhLjzIB0aPwbY4-QBcpjkhh9aFyUxYaZ8n_-ZE52WvXbCGcO9527VM6ggLLYOjQ?width=660&height=556&cropmode=none)
From the Race Tech website:
"Floating Rear Brake maintenance is commonly overlooked and can have a significant impact on a bikes suspension and handling. This type of rear brake was common up through the 80s on both dirt and street/road race bikes.

Now you might be thinking, "How would this backing plate have any effect on a bikes suspension?"

Well, since the brake "floats" it moves with respect to the rear axle as the suspension moves. This means that any binding in the backing plate bushing, or stay-arm pivots will inhibit suspension movement. This has a huge effect on both traction and harshness! This means that even the best suspension will work poorly when there is drag.

The main culprit is usually the Backing Plate Bushing itself. This is on the rear axle in the backing plate. These can bind for one of two reasons; first is simply neglect. The bushing is dry and/or corroded. Second, sometimes the dust cap on the outside of the backing plate on the axle gets grooves in it (over-tightening the rear axle or long-term wear) so when the axle is tightened it no longer has clearance.

Maintenance is pretty straight-forward; clean, inspect, grease. On the other hand, if the dust cap is grooved you will either need to replace it or figure out a way to get the clearance back (sometimes machining is required).

Next check the bearings at both ends of the stay-arm. These are all pretty simple; either spherical ball bearings, needle bearings or plain bushings. Take them apart, inspect , replace if needed, and grease 'em up.

You should be able to freely spin the backing plate with the rear axle tight and the stay-arm off. This is commonly overlooked and can reap huge rewards with a little love."
Cheers,
Alex
Title: Re: YZ125K Rebuild
Post by: alexbrown64 on January 16, 2015, 05:10:24 PM
Well, still going around in circles with some wins and losses.
One loss was the cases i purchased.  I never noticed, but the left case had been rewelded where one of the posts that holds the shift forks fits.  I posted it up in the tech section and got a bunch of good responses but decided to get another set flown over as they were only $35.  Hopefully, with the 6 case halves i will have, two will be good with an interference fit for the mains and no welds or repairs.  You could buy individual case halves from Yamaha so i dont believe there is an issue with "matching".

While i wait for the cases, suspension and new rims, i will pull the old wheels apart and start on the hubs..
Cheers,
Alex
Title: Re: YZ125K Rebuild
Post by: alexbrown64 on January 20, 2015, 10:58:02 PM
Well, the new GPI radiators arrived so i have given them a trial fit. Let me say, they seem reasonable quality and look great.  All the holes lined up and they fitted well.  The original large rubber grommets that are used to fit the rads to the frame need packing out as the original rads have a 5mm thick tab that the grommets slip into while the new rads are about 2mm thick.  Easy adjustment.  They also made up a yellow silicon hose set from an original set i sent them ( i never got them back ).  They look good and seem to fit well but i cant do the final fit up until i have an engine.  The have added a bit of "green" each end to allow for any inaccuracies.  Below are some pics of the rads fitted to the frame and the new silicon hoses.  I have also trial fitted the plastic scoop/shield things and the shrouds.  They fit well with some minor bending of tabs.  The only downside is that the old rads had prewelded nuts on the back of some of the tabs but the new ones dont.  I'm just glad that after 32 years, there is a replacement available.
Cheers,
Alex
(https://pkswgg-bn1305.files.1drv.com/y4mUhwi5E0Xlwmk0yygjaT-NDzhj9OOpNbae9g3d7uACrZPHNpQSKy4Moor2PCo-AbtJULkHrNtevW7cYWkUnSx4inS3LPjtj1dpD_CHwAUFxMWdYbxchg5GO6HN3rd4ylCja1kwG1hwgP0zMVonUbnfN9j3lFPcfu_5xlcdF1cHhGZXh3N3c3_J8m73wF1QsxjFcrU89Kmsis16z_bGbOAzQ?width=660&height=495&cropmode=none)
Title: Re: YZ125K Rebuild
Post by: foxy999 on January 22, 2015, 10:42:58 AM
looking very nice, job well done  ;)
Title: Re: YZ125K Rebuild
Post by: alexbrown64 on January 31, 2015, 02:42:15 PM
Thanks Foxy, its getting there... slowly.  Bit of a head f*ck this week.  Two steps backward.  1984 yz125 cases arrived in perfect condition.  Only thing is, they are slightly different.  I have another set of 83 cases coming so i will have a lot to choose from and keep some for spares.  I will sell the 84 ones as they have both cases in good condition, clutch cover and power valve linkages. 
Called RaceTech and they reckon one of my shocks i sent them is ok and they will send it to get hard anodized but they are really slow at the moment.
Have not heard back from Eric Gorr about my cylinder yet.
I have a bunch of stuff coming from the states. OEM front guard, Maier rear guard, seals, etc...
Local bike shop tried to order me some gold Excel Takasago rims for the YZ but struggling to get any.  I called Ash's spoked wheels and talked to Ash.  He said he has a front but they all need to be drilled to suit the drum front hub.  He is going to try get me a 18 x 185 rear but if he cant he will get me a 2.15 as he said you can still put a skinny rear tyre on it to suit the 125's.  That will also need drilling.  Both ends will also need bigger nipples to suit.  I have decided to send him the hubs and spokes so he can build them up and make sure they all fit up nicely.
I have blasted and painted the hubs and installed new bearings.  Wheel sets should last another 30 years if i do it right the first time.
I have fitted new Reed/Windham bend Renthal bars in black.  I fitted up the original perches and added new OEM levers.  Then i added new cables and pillow top grips.  I have always liked the Renthals.
So far i have gone through 8 case halves, 3 rear shocks, 2 sets of plastics, 3 sets of bars, 2 cylinders and tonnes of parts to try and get the bike race worthy and mechanically good enough to last another 30 years.
Pics soon when i have something to take a picture of!!
Title: Re: YZ125K Rebuild
Post by: Tomas on January 31, 2015, 10:29:01 PM
Like your thread Alex. It looks like you have already spend fortune on this bike. I am sure that you are going to keep this one for a long time. Any more pictures?
Title: Re: YZ125K Rebuild
Post by: alexbrown64 on February 20, 2015, 12:30:48 AM
Tomas, as promised, some more pics.  As usual, the bike is fighting me all the way.  I finally put together a decent set of case halves.  When i chose the two best ones i had out of the 8, i removed all the bearings and seals.  I then used paint stripper to strip away 98% of the paint.  When i was happy, i put them in my Bunnings home sand blaster and cleaned them right up.  Then i washed them in detergent and used a compressor to blast away any remaining grit and to dry them.  I then put them in the oven at 100C for an hour.  During this time i got all my bearings ready for each side.  I then inserted all the bearings using a combination of G clamps as presses and sockets to gently knock some into place.  I used all my pictures of where each bearing goes as described previously in this post.  Righto, all bearings in, so i put both case halves together, clean them with wax and grease remover then use my aluminum engine paint to give them a nice coat of silver as per the Lechien OW125. (i also had to do a lot of prepping and taping up).  The cases looked great but to cure them they need to go in an oven at 100C for an hour.  So, back into the oven to cure it all up... pic below...

(https://000hmg-bn1305.files.1drv.com/y4mLDhlkT8-CvAWeZXIGSA_wCk4NOr5xGd3jhceux9MM7c1XBSQDZS74Odqe14-Wva29k_c7ESEeziePfJBDRqWG5tQoN-ZqOUPt0lBLqjPoBZjUNg0nRhpfS9OBC06_bYa8WGY3fR-vC2Y7R-ZDQX3-Vv5GfAx3XrCTW2iAnNhkNLiW2gjMwpVuZG3uKWNH1ormez1o0hdlKhKKNUURjlYTw?width=660&height=495&cropmode=none)

Now there is a thousand ways to skin a cat and this is just the way i had decided to do it.  When it was all cooled down, i took off all the masking tape and spent some time inserting the main seals.  I will leave the other seals until i get it together.  You can see the pics and manuals i used to make sure i was getting it right.

(https://002gvq-bn1305.files.1drv.com/y4mDx82XhlrjoE3MGvQ4bXHenjYTrrb4_knRr5TMuKUElw2AQZQ5jQAB2ymuX9qU8TaKFx9fGZAkfJKrAYyVCJOK-CJTNYNV7xLoGzUheNuHN4rSKLTnR1QQdp66VNCkSo-lHhoa2get5IEtq55_g49f7w0H5hPpNgTSgiUw_ho83v0sBAVaPV3YVIbREGYIyXkJQvZVrhK0zLdNtkUjd0jEw?width=660&height=495&cropmode=none)

OK, now down to the nitty gritty.  I checked all my pics, the manual etc, and installed my gearbox. I could run it through the various gears from 1st to 6th so i was happy it all went in OK.  The next part i picked up on YouTube.  To install the crank, i heated a socket on the stove and then put it in the main bearing.  The heat transfer expands the bearing and the crank just falls into place.  This went well and it just fell into position, no hammers, pullers or anything.  When i was happy with the crank and gearbox, seals and everything, i prepared to join the halves.  I used the same trick to heat the bearings in the opposite case so that it would just fall together.  While the bearings were being heated, i slapped Three Bond on the cases as the gasket material.  I then positioned everything up, made sure the dowels were in and then popped it all together... pic below of it all happening...

(https://003rsa-bn1305.files.1drv.com/y4ms2ZfjA6NIww2tYX-qI-PNcK_RLjw2u-joEoQQLkl8Kn-t9rxbzRxOV3nEv8kzF-hkMOfNlxyQkeENR_WKPbx8s0WFT2DDHVKVxFFg_6P7rq_cR0A4V4ugXUwOS1o1uE3b18G1F9CpHO_bbYF6v9sFgVBEqu8vgMZfgd7kX3QVbazgavdBl6zZ5TxLwmWU8lw6AMVAgFY3oZobkojUCCEcQ?width=660&height=495&cropmode=none)

It all slipped together easily... and i nipped everything up with the new engine bolt kit that i had bought.
This is where it all went wrong.............

When i nipped it all up and the cases were tight.... so was the crank.  I loosened off the bolts and the crank loosened up.  I tapped everything and had a play all to no avail.  It all had to come apart again.  I have another post in the forum on this subject, but what had happened was that when i had the crank rebuilt, it was rebuilt 1mm wider.  This meant that it would get tight in the cases when you did the final nip up.

I took the crank back to the shop and they pulled it apart.  It had been damaged previously so they were not able to use the thinner shims that had been supplied with the ProX rod kit.  The shop machined the crank and put it all back together using Yamaha crank specs.  Thanks to Witch Cycles for fixing the problem and not charging me any extra for machining etc.. 
Also, when i tried to remove the crank, it was really stuck in the cases.  I *ucked up and belted it out and bent the tip of the shaft and damaged the threads where the rotor goes on.  Before i gave it to the shop, i straightened the tip up and cut off the damaged threads.  It came up like new so i got away with it just this once.

And that is it for now... tomorrow, i clean up the case halves and go through the process again and hopefully this time it will all be OK.  I hope to get it all together and in the bike soon.

On another note, Eric Gorr has completed the cylinder sleeving and porting and has sent it all with the new 56mm Wossner piston kit.  But for now it is going back together with my 58mm Wiseco kit and my original cylinder.

Cheers,
Alex

Title: Re: YZ125K Rebuild
Post by: alexbrown64 on February 23, 2015, 12:06:26 AM
Got stuck in and managed to get a bit done.  This time, the case halves went together easy and i buttoned it up with my new SS bolts. 
(https://0021xw-bn1305.files.1drv.com/y4mAVlwHTry5gCS2_kwlxC5yTNuF-hCgY5AqzEjZj7iyr6MBUqXKypbhCw8SW_1tFwhNZe8FrXBtJjjBS0SXegRkUBw6eRxIf2NzDG7uRLc2lSR5R-tB4RNb020oDrW6siTrEj5mVJvY2qUz4mpOYtNpTKgrwwwLA418DNeOor7VMYuVMiHh84J5577A98L8hFOWpyFHw28bLt2Cx6Eq2RntQ?width=660&height=495&cropmode=none)

Next up i fit the clutch arm shaft.  This take an hour because it would not go in.  I sanded the internal shaft, cleaned it all up and it fitted.  There is a new bearing in there and i put the seal in before i fitted the shaft and tapped the retaining pin back in.  I forgot to put the spring on but managed to work it over the shaft arm and into position because i could not get that retaining pin out again.  When that was done, i fitted some gears and things and put the clutch back together with new springs and plates.  I also put a new gear shift shaft in and tested it.  Gears work well.  Also fitted the 58mm Wiseco piston with a new small end bearing, ring and piston clips.

The cylinder, head, power valve and PVL ignition were fitted and torqued to the correct specs and then the timing was set on the bench using my home made dial gauge set at 1.2mm BTDC.

(https://ctcyeg-bn1305.files.1drv.com/y4mBWREX63jqXg2-nUNJYbBPpUqU2Lv5HhJjbvkXOxn97xFzP6BIc-Vbotkujq_g2acwkky682oO5sVhSaSo8OKhCCIK06L3z9CuURgzFqqSFbtS_WWixb7JH0ZHMEQ3R7YXM6NgOJlzwspuXSWK0UuSc3NEn1firnC2C57pXpVoNs4tZfPcw0_vbA9FeiyTfcHVZjgH8BZNs5S9M416rxKUw?width=660&height=495&cropmode=none)

I used the old grommet from the original ignition and fitted to the new cable coming out of the right side case.  I had to split it, then reseal the split with rubber cement.  I then fitted the kick start and sprocket shaft seals.  Next up was the new 12 tooth JT sprocket which was torqued up to spec and a new washer with a tab bent into place for safety.  The engine is now ready for fitting.

I cleaned up some engine mounting threads and filed some paint off the frame in preparation for engine fitment.  The engine went straight in with no problems and i fitted up the polished engine bracket with new bolts.  I then fitted up the ignition cover and clutch cable.  I had to leave the clutch cover off before fitting the engine because you have to fit the clutch cable and then undo the lock nut on the clutch center and play around with the clutch centre rod and clutch shaft arm position.  Thats all explained in the manual, which i constantly referred to in conjunction with all my pics i took.
After adjusting the clutch and doing a few other bits and pieces it was time to call it a day.  Below is a pic of the fully rebuilt engine finally fitted into place...

(https://2pqoyg-bn1305.files.1drv.com/y4m8ZzmsxHIi4ktuaphfb3PG5gbaMYvf0OkHlWZmIyMxU2z7tIqaxzWHUsXGOSoMhZbbtB_-6-rXHSf8GX0tvS0tqLCJ5dlRonFWfcvltTD8l_V3F8uFSZCwVHUYkEjIXqodB6xrBRQRgUhUmCap9Mjr4VhPp5_z5ydrpXW_7v88ltyifxuCm5BQJdxnfTlo-3PSdaQlLpv5v7nu9dynVydUA?width=660&height=495&cropmode=none)

The YZ125K engine was originally black, but the Lechien works bike had a magnesium coloured engine which is what i painted mine.  The cylinder and head have been blasted and clear coated with VHT engine clear coat.

Cheers,
Alex
Title: Re: YZ125K Rebuild
Post by: FourstrokeForever on February 23, 2015, 09:55:42 AM
Looking good Alex. It's such a great feeling to have a better than new old bike that you build yourself. And the confidence to know that everything is done right. Top job mate.
Title: Re: YZ125K Rebuild
Post by: suzuki59 on February 23, 2015, 11:23:13 AM
Looking great mate !
Title: Re: YZ125K Rebuild
Post by: alexbrown64 on February 23, 2015, 01:18:31 PM
Thanks for the positive comments fellas.  Well, i have had a bit of a play and got the clutch cover on. Its a bit of a rub your belly and pat your head at the same time type of job.  Insert the power valve governor into the side cover lining up the power valve linkage and governor groove.  Make sure you have gasket and dowels on case and all water pump gears in.  Put side cover on and align water pump shaft with white plastic gear by twisting the pump shaft.  Then make sure governor gears mesh by gently moving kick start while pushing clutch cover into final position.  Then it was time to bolt up the power valve linkage and adjust it as per the manual and fit linkage and water pump covers. 

GPI Racing silicon hoses:  I sent GPI a set of old hoses, photos, diagrams and the like and they made me up a set of custom hoses for the YZ125K.  They now sell them on Ebay.  I asked for them to be made in yellow as i have never seen any like that before.  I used my existing clamps to fix them on and all i had to do was trim them down an inch or so as GPI leaves a bit of green on the ends.  Better to be longer than too short. 

Below is a pic of everything fitted up.  You can also see the airbox mod i did which is specified in the Yamaha tech report.  Drill 4 x 25mm holes in the airbox for better breathing.

Cheers,
Alex

(https://nwsisg-bn1305.files.1drv.com/y4mQ5gG2ZOB4U-5scHQfdRXsrRbNUDNMENUUd8T5bg6k9ykCbOsWP3BdPSGLGrjmwMjSszIZr0lLb0h4pJzCHJs6T98aNbqY6VO02yQD88v4NVwkyVckcaSHlqcwFgPEMLBNebyyxpSQ9Lb6RZc3eaNaAj-P9wFMfrVNQISeohd7Jpl4rSHFg416vT8Ye_fRaIMZtSfJLxaD46Njre5_Ykuzg?width=660&height=495&cropmode=none)
Title: Re: YZ125K Rebuild
Post by: smed on February 23, 2015, 05:06:23 PM
Looking good Alex, top job mate ;) I used VHT clear on my head & cylinder on my aircooled CR250 after it was blasted, I cured the paint in the oven but found every time the bike was ridden the paint softened up & dirt stuck to it & made a horrible mess,exactly the reason I had done the clear in the first place,to stop dirt sticking >:( >:( >:( >:(, I had to rebuild the top end after a seizure so paint stripped the stuff off, Now it's all good & easy to clean, you may be OK with a water cooled bike as the temp may not be as high :)

Your gonna love riding this bike,nothing like an old flame 8) 8) 8)

Here's mine :)

Circa 1985

  (http://i1266.photobucket.com/albums/jj529/smed45/2011-11-01_22_zps54ac3547.jpg) (http://s1266.photobucket.com/user/smed45/media/2011-11-01_22_zps54ac3547.jpg.html)
(http://i1266.photobucket.com/albums/jj529/smed45/2011-11-01_27_zps2f55781c.jpg) (http://s1266.photobucket.com/user/smed45/media/2011-11-01_27_zps2f55781c.jpg.html)

Not the same bike from back in the day but near enough,same year model ;)

(http://i1266.photobucket.com/albums/jj529/smed45/IMG_1064_zps815ff58c.jpg) (http://s1266.photobucket.com/user/smed45/media/IMG_1064_zps815ff58c.jpg.html)



A couple of years back at the Broadford Bonanza on the above :)

(http://i1266.photobucket.com/albums/jj529/smed45/9e8a59dad7_zps69c779f1.jpg) (http://s1266.photobucket.com/user/smed45/media/9e8a59dad7_zps69c779f1.jpg.html)
(http://i1266.photobucket.com/albums/jj529/smed45/hbbb2012121_zps9ce6c6cb.jpg) (http://s1266.photobucket.com/user/smed45/media/hbbb2012121_zps9ce6c6cb.jpg.html)
Title: Re: YZ125K Rebuild
Post by: alexbrown64 on February 23, 2015, 07:01:18 PM
Nice pics smed... i see your still running the same number.  Good looking bike, do you still have it?  I had the 81 CR125 -  first watercooled one.  What a turkey... it put me off Honda for a long time... so i bought a YZ125J then next year.... what an unremarkable bike.  The K i am doing up was the first bike i really gelled with so i'm hoping for the same again.  I will see how i go with the clear coat.  This cylinder is only temporary until my new ported Eric Gorr cylinder arrives and they just bead blast them and leave them bare.
Anyway, ive got some time up my sleeve so jumped into the shed again and had a go at fitting the carb.  The Yamaha Tech Report called for an upgrade to a 36mm from a 34mm.  Ive got some info in the thread about jetting etc.. so this new VM36 was jetted as per Race Report.  I had already bevelled the inside of the air filter boot to help with installation and ive trial fitted it before.  But there was no way it was going on today.  I wrapped the carb up and cut 15mm of the large end with a dremmel.  I then bevelled the intake to make it easier to get on the boot.  This worked a treat and i was able to get it on and get a good fit up.  I then got the cone pipe re-fitted the engine and hooked up some wiring.  The pic below shows the new VM36 connected as well as the PVL system and a new hour meter.
While i am waiting on the suspension and wheels, its just doing all the nitty gritty.  I will repack the muffler and get all the plastics fitted up properly.  Also, check for spark and maybe kick it over and get it running.
On another note... i tried to fit the gear shifter that you can still buy as a Yamaha genuine part.  What a con.  They are made of cheap pressed steel and are not the correct shape anyway.  They sit too low and dont have the correct bend thus hit the clutch cover.  I tried bending it out and it cracked... I just chucked it in my scrap pile in disgust.  Ive had my eye on an aluminium OEM one for a while and it was still on Ebay so i grabbed it.  I will give it a good polish and i know it will fit well and look the part and be stronger than those things that Yamaha are trying to pass off.

Cheers,
Alex
(https://2psuaq-bn1305.files.1drv.com/y4m5gMDU67NnFqu2CoHQDLj5EMacAhstgOOY_Pkgi2C-Ft_6Fg-wp1_Audk27ylPeam_15vAeyK534rorE-89pfUg-UP6Frxk4NAvH1tN7KcScuVzrldkVdvI8hwqA7VeT6BbWs5q6cxTgsiGfB7xtrJ0AXyjzlPfQtzNuPfskY38So27IN2j143A6lB3Tm21wRnR-_t1UfG358NBnuh3axCA?width=660&height=495&cropmode=none)
Title: Re: YZ125K Rebuild
Post by: smed on February 23, 2015, 08:48:00 PM
Nice pics smed... i see your still running the same number.  Good looking bike, do you still have it?


Yeah just dropped off the 3 from the early days to make 45, Still got it, It's a keeper ;)
Title: Re: YZ125K Rebuild
Post by: alexbrown64 on February 25, 2015, 03:07:25 AM
This one will be a keeper too Smed. The boy can have it when he is bigger.

Got stuck in tonight and did 5 hours straight to try and get through the punch list.  Radiator shrouds were fitted properly and the radiators filled with glycol.  Muffler was repacked and refitted.  Side number plates were heated and fitted properly to clear muffler and sit better.  A bunch of works washers were used all over the bike to give it a factory look.  Front brake cable guide and sprocket cover were fitted.  Special washer made for swingarm bolt and then torqued up to 60 lbs.  New OEM pins fitted to footpegs.  A mounting plate was made for the PVL CDI unit and then siliconed and bolted together and then mounted to the frame. The new UNI airfilter was oiled and greased and remounted. 

Bike is now ready for suspension and wheels.... Ash's Spoked wheels is getting my nipples anodized gold and ready for the new Excel Takasago gold rims.
Im still waiting on Race Tech as they sent the shock body away for hard anodizing.  Next pics should be of the bike completed....

Cheers,
Alex

(https://2ptk6g-bn1305.files.1drv.com/y4mxeWymujuF7UpGtTV07UNQv0NeelUWV_oiofyYVjMLVIv3DItdfUKXwyP0RTOsEHdz9zPthlJ6b1VbE5txif_ByHjpSiq40PrhazIusg7L7cblm6k1XfZ6lahDZnq_SI3Urg7WW6VGX213wHp8aMcqElYVW4uflJnwztPPC7fqd94UuTI9iuF_jjgUEpnnc9TWxVa94KdLFy4Zz-y2ypBdg?width=660&height=495&cropmode=none)

Title: Re: YZ125K Rebuild
Post by: alexbrown64 on February 25, 2015, 06:42:15 PM
Put 850cc of MTX 80 gearbox oil in her,  a litre of premix at 25/1 and tried to lower the bike down on the hydraulic bike stand.  The hydraulic part is knackered but it has a locking bar.  I took the weight a little and removed the locking bar.  My first crash on the bike.  It came down so  fast and it nearly took my fingers with it.  Result... bike on the ground with bent front brake lever and two bloody and bruised fingers.  After some ice, panadol, setting the bike back up and straightening the front brake lever and checking it all over i kicked it in the guts.  Started 4th kick.  Lots of smoke coming out the muffler and black splooge coming out between the pipe and cylinder.  Bike is idling well and revving well.  It does seem to vibrate a bit more but im not sure if its because it has no wheels and tyres on.  Also sounds a little deeper and at the moment is not revving entirely clearly and freely.  Still only first 5 minutes of running from a total rebuild so not sure what to expect.

Phoned Shock Treatment today and the anodizers will not anodize the shock body.  Something about the design and how they cant guarantee the work.  I cant seem to get a break.  He said the shock body only has signs of polishing inside and is not worn.  Not sure what to do... they said they are looking into a race tech full shock.  They can also rebuild the good shock  without hard anodizing and they said it could last 10 years or 10 minutes.   I may also contact Wasp about a shock... 
Cheers,
Alex
Title: RRe: YZ125K Rebuild
Post by: mick25 on February 25, 2015, 07:37:06 PM
I have the same Yamaha bike stand as yours I got it cheap second hand it's a bit worn out because it's made out of alloy but it's not as good as my red steel ballards one that looks and works the same but better ?
Nothing worst than a bike falling off a stand .
Title: Re: YZ125K Rebuild
Post by: smalls717 on February 28, 2015, 01:28:41 PM
Looks good Alex... What was the time frame between sending your radiators to GPI and getting them back?
I'm trying to get a set for my 84 KX250. One model only radiators and no one makes them.
 8)
Title: Re: YZ125K Rebuild
Post by: alexbrown64 on March 02, 2015, 06:08:18 PM
Smalls, it took about 4 1/2 months from when i sent the drawings and radiators/hoses until i got the new ones back.  Long time and not sure what happened but its done.  You will need to find a knackered set to send them.  I have provided the contact details below.  If you want to take that route, then contact them by email first and ask if they are willing, giving all model details.  Best thing to do is find an old shonky set on Ebay, and get them sent directly to GPI and then wait.......
Cheers,
Alex

To: gpiracing@126.com, gpiautoparts@gmail.com

our address:
sheng hua shang du 2404# ,wen shao lu 19#
zibo linzi shandong 255400
china
receiver: wang yu ping
phone number : 13011631781 (very importance)
you can find  a little bigger box ,so  you can ship the radiators and hose with one box .
pls write parcel value is 30usd .
thanks
gpi




Title: Re: YZ125K Rebuild
Post by: alexbrown64 on March 11, 2015, 12:11:41 AM
Can see the light at the end of the tunnel now.  Takasago wheel set arrived today.  Got the bike shop to fit new tubes and rim locks together with the nearly new Dunlop tyres.  Managed to fit the rear up with a 50T alloy sprocket and a Regina non - o'ring gold chain.  I also whipped of the short tubes that came with the VM36 and put extended yellow tubes on.
The suspension has been built and is in the post.....
Cheers,
Alex
(https://pyd0pq-bn1305.files.1drv.com/y4mYaINg81dokphUWFlO5VcsI586p5Aa64TsCR_DXyxkX2UyiM8ufuhL3-Hx7VoRbv772niRIk0SCCs7Z_09K-vJj9Lyik-ct5S9NZnIn4kr6u2TBBYQcPisIP2VFPS1QZ5tfdcrR23gap4Uyn0-OSCIcX8zXogS8CCgdQe0c5bUMAXbPgkuoZ0-1c4XjXGau8C3l58jLaRKQBsqy-xxmglzg?width=660&height=495&cropmode=none)
Title: Re: YZ125K Rebuild
Post by: alexbrown64 on March 11, 2015, 10:23:06 PM
Getting to the nitty gritty side of things now.  Bike should be up and running next week so it will time to tune the donk and setup the suspension.  For anyone interested, i thought i would post up the articles that i have been basing the rebuild on.  Besides the Lechien look, i used the April 83 edition of MXA for idea's as they printed a hop up page for the 125K.  This was updated with the May edition of the Yamaha Tech Report which refined the hop ups and specs...
(https://pycpva-bn1305.files.1drv.com/y4mle5ystCq4N9LzH8WeQZZRwOM6LktyJAdjU78PEi026bBDCq2mvG1ygsngDVTuTVa-mZI9KUxzcx9hcddrl7GJ1-HC1v8C3voHFYsfRQGkCmWS6jt4SnwvFxg99yHZaNrp509vf9srEhsM5yktkfVym9cWco5AJjFlnW2OJ8shAhgMF8m3a--fZm1lRY9XLI-t_Vv87hsRXhiDnMVWTIZkg?width=503&height=660&cropmode=none)

(https://pyajsa-bn1305.files.1drv.com/y4m4apCKYS3G4Uju1NOOY2-2ulHBruJEMgXTJ4YYHA0Mh-pjEtNtPSotv-h182H42QQUatWWeOk0EzCpFvBvQTEMWRosHqKSGojEonQTSUVsNEZnX6_I2TH8e1m4nO5BH44Gb4GYH4MI7byFPnRGXE0CYOUDZvojqtpA3T9_7bu5BV-34ReB7tOPEe37gLSesiXMthtYqHEB_3EMJjVNw5w5g?width=504&height=660&cropmode=none)

Cheers,
Alex
Title: Re: YZ125K Rebuild
Post by: alexbrown64 on March 15, 2015, 07:47:30 PM
The Lechien bike had a Dual Leading Shoe (DLS) front brake, but the 83 125 didnt come standard with one.  They cost a small fortune on Ebay.  While keeping an eye out for one, a YZ125K popped up, which is rare.  It also had the DLS front brake on it.  Anyway, apparently it is a good runner.  I purchased the bike and it is on its way to Perth next week.  I will swap the DLS front brake onto my Lechien tribute 125.  The Euro model will be cleaned up and used as a practice/fun bike.  Hopefully, it just needs a good clean up, decals, fork boots and the like. 
Cheers,
Alex
Title: Re: YZ125K Rebuild
Post by: Rossvickicampbell on March 16, 2015, 01:56:45 AM
as big as I am I had the opportunity to ride a fully restored YZ125K - I bought if for my sons - and it was a dream of a bike - loved it.
Title: Re: YZ125K Rebuild
Post by: Richo52 on March 16, 2015, 09:30:09 AM
Yes that bike was awesome Rosco ,you let me ride it at Beverley ,it went really well.
Title: Re: YZ125K Rebuild
Post by: alexbrown64 on March 18, 2015, 03:25:28 PM
Cheers fellas, yes, i think they go well and so light.... i cant be arsed trying to lug a tank around the track any more.
Anyway, finally got the Race Tech suspension back......

(https://pktmaw-bn1305.files.1drv.com/y4mNz_lL69iiUxfAMOJqxKO26nkRWcV55TRijrgWYatOcK5eyvWYPrUyh-fRF6Kn9-pFZtOAgbkhtoYmjWCuY8ptFa7FEK7oS2Z44NQaPZdur56Z8sfKaQyM2q6M6KHTSB8ILJx4EkAIbLpR7A0SdXu-VsHW5ecpq9wkwCcytDaWm0VOE8PaliW7xU4oqpYu_ghNzssCS3KviHCWCXhaVziww?width=660&height=495&cropmode=none)

Finally i could take it out for a photo shoot.  The bike is going to need lots of small adjustments.  It needs to be run in, tuned up, suspension set and a host of other bits and pieces but its a runner now.....

(https://4dvalg-bn1305.files.1drv.com/y4mTcnM3DMsGNT_b22h6PErPmE235rXpxKNMk0E5fpwRvaKBt4ZK2IYq1nXSDRZm3bkYFbpFaDhSnaMmbA1MKaFkGPqkipu3s_YKshoAJ2dszXzzIDIkpGk0Bl5l1aVrwEzIOBv_-lGHPJNs04Jv6COwXnjGeIl2OrEe_Gefn311diRXOq4PH7mi0jUBIn7yK_zDWFkyxp5v3U1XaPUhPP0KA?width=660&height=495&cropmode=none)

(https://pycpgg-bn1305.files.1drv.com/y4mEp91QzNYIb31ihe791_L9vFVynkNeHv4eHikYvz-EnVxCOCa-xNvEz4-QK62bZ5y0j_f1qgbncQLqzvWVq2cghaVTvlr6UeQ1NW4_bLdb5N3__q-80LAka49npdbcXcT0xTbflCi3tzdCNryS6m9D9kpjtxQtGjtSdqvOHluUKr7LCkHin9MW4V1TLviHYkeZvTcAYkQ0E4C4mWXQiQwUQ?width=660&height=495&cropmode=none)

(https://2pqvdg-bn1305.files.1drv.com/y4m5FkLK_2iojnQbwu3VPEvFkf7nPVvhRUHLwQ9_bzQqpmF1FnfKJ57Odi15I9fMzVcB3ES2OXLtv4DrT7VgF0Vtx95vLCQaPP6hOyW2Gitfgd3ixvfUoO5BqeJVKc9tv-u7WPoEg1W7gciVFeUQEDgVmVbJGLYI0gmWA0GwSRmbaH-jo_hzIcTrcYwqz0S8EbhxzVQNi1hspuf6CT4Xglzig?width=660&height=495&cropmode=none)

Project completed...
Cheers,
Alex
Title: Re: YZ125K Rebuild
Post by: smed on March 18, 2015, 05:15:03 PM
  The forks feel stiff at the moment.  Maybe they need running in, maybe they need adjusting....



Alex,I put a set of race tech emulators in my 43mm Yam forks set up similar to yours with springs to suit my weight,new bushes & seals etc & found they are stiff feeling when bouncing on them in the workshop but near spot on when riding,a test ride will tell ;), I have found modern forks to behave that way too, those emulators really emulate ;D ;D ;D
The bike looks awesome,Are you putting on number 224?   
Title: Re: YZ125K Rebuild
Post by: alexbrown64 on March 18, 2015, 05:44:22 PM
Thanks for the feedback Smed.  I will take it bush soon to run it in and bed all the components down.  I think my spring preload may be up around 15mm.  Recommended for this bike is 5mm.  Race Tech says make changes in 2.5mm increments.  Just wondering if that can make it feel a lot stiffer when just sitting on it.  The new back shock feels perfect.
As for the Lechien 224 numbers...  i may put some on when i get the DLS front brake and everything is finished just for a photo shoot. I will be re-registering with the MWA soon so not sure if i can score that number.  I doubt it... to old and slow now.. i think they reserve the 900 numbers for guys like me.
Cheers,
Alex
Title: Re: YZ125K Rebuild
Post by: Ted on March 18, 2015, 06:03:56 PM
Very nice job. All it needs now is Ron to sign it. Stay tuned  ;)
Title: Re: YZ125K Rebuild
Post by: 80-85 husky on March 18, 2015, 06:06:50 PM
Another work of art ;)
Title: Re: YZ125K Rebuild
Post by: mainline on March 18, 2015, 08:59:40 PM
Very schmick mate, great attention to detail
Title: Re: YZ125K Rebuild
Post by: Rossvickicampbell on March 18, 2015, 09:07:09 PM
Alex - if you sign up for Classic MX WA whole different numbering system now - certainly not 900 competitors there yet  ;D
Title: Re: YZ125K Rebuild
Post by: FourstrokeForever on March 19, 2015, 08:17:28 AM
Great work Alex. You sure do know how to bring a bike back to life. Well done
Title: Re: YZ125K Rebuild
Post by: r4brightred on March 19, 2015, 10:53:51 AM
Pure eye candy! Nice work.
Title: Re: YZ125K Rebuild
Post by: smed on March 19, 2015, 05:55:54 PM
  I think my spring preload may be up around 15mm.  Recommended for this bike is 5mm.  Race Tech says make changes in 2.5mm increments.  Just wondering if that can make it feel a lot stiffer when just sitting on it.

Yep, that's what i'm thinking  ;), I used what  Race Tech called there  triple rate spring kit  to suit my weight which I thought meant just that, a progressive spring but when I opened the box to my surprise I found 2 long springs & 4 short springs which were about 50mm long, On reading the instructions it all became clear,The long spring alone is the stiffest rate 0.46, the long spring + 1 short spring is 0.43 & the long spring + 2 short springs is 0.40, I needed the 0.43 set up according to them so that's what I fitted, The kit also came with spacer material which seems to be  thick walled PVC, so you just calculate how long they need to be & cut to suit, I will use this type of kit again if I need new springs for another of my bikes because of the tunability :) 

  (http://i1266.photobucket.com/albums/jj529/smed45/T%20amp%20M%20%2076%20017_zpsojsjansa.jpg) (http://s1266.photobucket.com/user/smed45/media/T%20amp%20M%20%2076%20017_zpsojsjansa.jpg.html)
(http://i1266.photobucket.com/albums/jj529/smed45/T%20amp%20M%20%2076%20016_zpsykw1ym72.jpg) (http://s1266.photobucket.com/user/smed45/media/T%20amp%20M%20%2076%20016_zpsykw1ym72.jpg.html)
Title: Re: YZ125K Rebuild
Post by: alexbrown64 on March 19, 2015, 07:29:49 PM
Thanks for the comments fellas. 

Its been flat out but worth it, as i hope to race this one in the future and then keep it for the boy. 
Anyway Smed, and anyone else that has been playing around with the emulators.  I was lucky in that i found a bloke in the US that used to race this model and he gave me the contact details for Matt Wiley at Race Tech in the US who in turn gave me all the settings to use.  Smed, i also have the .43kg springs in. However, initial feel on the bike gave me the impression the rear was great but the front was really stiff and there was no sag.  Forks apart again and the first thing i did was take the emulators apart and drill two more holes in the bleed valve.  Mine only had the standard two, but Race Tech recommends four holes in the bleed plate.  This softens up the initial stroke.  Then i reset the preload. I had nearly 15mm which is way too much.  I reset this to 2.5mm.  Got it all together and what a difference.  If i sit centrally up near the tank and bounce up and down, the bike goes up and down evenly and nice and smooth.  I now have some sag in the front and everything feels balanced.

I wheeled it out the shed and fired it up.  Took it for a ride around the garden and all good.  Brakes, clutch, gears, everything smooth.  Bike runs well but a little oily and a lot of splooge coming out.   Its early days though and i will need to adjust the air screw and run it in.

Cheers,
Alex
Title: Re: YZ125K Rebuild
Post by: Lozza on March 19, 2015, 09:10:31 PM
I like to use acorn/domed nuts on head studs with copper washers underneath. Nice job. Have you burned/shredded all the  receipts so the Mrs happen across them ;)
Title: Re: YZ125K Rebuild
Post by: alexbrown64 on March 20, 2015, 07:13:00 PM
Thanks for the heads up Lozza.  I stopped in at Masters and got some 8mm SS domed nuts.  Copper washers are harder to get.  Want 8mm x 16mm x 2mm.  Masters didnt have them, or Repco or the local bike shop.  Ordered a pack of 20 for 7 bucks delivered, correct size on Ebay.  Not sure what i would do without Ebay these days.  I have also ordered some YZ80J exhaust gaskets which are a much thicker material and recommended for the bike in the old magazines.  I will do all these mods together as i have to take the pipe off to cut down one of the cylinder head studs which is a bit long.
I also got an email back from Jon Easton who runs the Jon Easton Manufacturing Co. (JEMCO), who hand made the cone pipe.  Gave the bike the thumbs up.
As for the receipts, i would rather burn and shred the missus first   ;)
Edit: The bit about the missus is a joke... please dont try this at home  ;)
Title: Re: YZ125K Rebuild
Post by: 80-85 husky on March 20, 2015, 07:30:18 PM
I would seriously modify that last post Alex ::)
Title: Re: YZ125K Rebuild
Post by: alexbrown64 on March 20, 2015, 08:14:14 PM
Whats wrong with copper washers Husky?  ;)
Title: Re: YZ125K Rebuild
Post by: FourstrokeForever on March 21, 2015, 07:56:45 AM
Yeah....nothing wrong with copper washers  :o
Title: Re: YZ125K Rebuild
Post by: 80-85 husky on March 21, 2015, 08:43:34 PM
copper washers fine, comments about burning could easily be misconstrued by the jury..... :o
Title: Re: YZ125K Rebuild
Post by: alexbrown64 on March 21, 2015, 09:42:28 PM
I edited it to reflect the fact that it was a joke Husky... wouldn't want anyone to think i go around burning missusses  ;)
Title: Re: YZ125K Rebuild
Post by: 80-85 husky on March 22, 2015, 03:20:46 PM
good move ;) now back to that bike....
Title: Re: YZ125K Rebuild
Post by: BJJ on March 26, 2015, 08:12:42 PM
Very nice looking Bike Alex,  and thanks for sharing all these tips and information on the things that you learnt lessons from.
Title: Re: YZ125K Rebuild
Post by: alexbrown64 on March 27, 2015, 12:56:16 AM
Your welcome BJJ.  I get good advice from the members on here and these builds give everyone ideas.  I also keep the website updated with all the updates, parts, articles, tech document etc.
www.yz125k.weebly.com

Cheers,
Alex
Title: Re: YZ125K Rebuild
Post by: Ekka on March 27, 2015, 10:05:30 PM
Very nice job Alex 
Title: Re: YZ125K Rebuild
Post by: alexbrown64 on April 01, 2015, 06:07:08 PM
YZ125K Ride Report:

Day one, got into the bush and went for my first ride on the bike.  I have warmed it up at home a few times but i still needed to run it in under load, so i puttered around a bit.  First pic shows the setup i have for getting it all out there. Intial feel of the bike was great.  Suspension worked well and bike felt good.  A lot of smoke and spooge coming out but i need to open it up a bit to find out whats what.  OK, second pic is a minute before bike broke down.  I took off again and got 20 seconds down the track and it died like when you run out of juice.  Checked fuel tap...noop. A wiggle here and a look there, but she would not start.  Pushed it back to car and went home to wash her down and investigate.  Ended up being NGK Iridium plug.  Just 30 minutes old and packed up.  Maybe because of the oily bike.
I checked timing.. a bit off.. it was 1.4mm btdc.  I reset to PVL recommendations at 1.2mm.  Next was the spooge. I had put a 50 pilot in as thats what the Yamaha Race Report said was the hot ticket for the upgraded 36VM.  The modern day 36VM comes prejetted with a 35 pilot.  I put the 35 back in and at 1 - 1.5 turns out it cleared up the roughness and got rid of the smoke.  Time for another test ride.

Day two test ride. Started first kick on the choke and run well.  Took a minute to clear its throat and then we were away.  I gave it a half arsed attempt at final run in but it was good enough for me and i started opening up.  Bike now rips.  Still needs some jetting but getting there.  In first it can sound like four stroke valve bounce when i rev it hard sometimes.  The suspension is great and really handled the whoops and sand.  I have not hit any jumps yet so my forks only showed im using about 7 inches of the 12.  I may have to take a whisker of oil out of the forks if i cant get full compression.  Photo 3 shows the tracks im running.  They are all whooped out everywhere.  On the long fire tracks i could get 6th gear wide open on the whoops and the bike felt really stable.  Fourth photo is when i noticed radiator fluid coming out the overflow.  It wasnt steaming, it was just coming out.  I headed back to the car with another 30 minutes of testing done.  The rad needed 350ml of fluid when i got home. I'm not sure if i had the cap on tight. I will take my genuine cap and some fluid out with me next time.

Brakes have bedded in and i have now used up all my adjustments.  So i have to pull the levers off at the hubs and move them a couple of notches.  Bike now needs checking over, tightening everything and getting ready for another run.
(https://4dvhdq-bn1305.files.1drv.com/y4mQ8R4AX4e6lGl0lb03xoy4xNDTDIWXj3GrACEkINgaBkAoHXGKOJBJDQwbNPcIUp-l24apej1BpawrlXO1caxkIeAAcmB_HYUo6yvwu2SBsIoUDMbrVdTEUpoU8CZNmnwF3zGwnvZ5iZ5O-cLszvAaz9MefNi2zY54daAXvOHFJ4g0sVWaGXXj48Xq4Xw94xqkHIm5QEaWzG-hHOXfYqX_w?width=660&height=495&cropmode=none)


Cheers,
Alex
Title: Re: YZ125K Rebuild
Post by: mainline on April 01, 2015, 07:27:19 PM
Sounds like a good time was had.  I hope you told someone where you were going, that looks a long way from nowhere if you were laying around waiting for someone to come and pick you up off the ground.
Title: Re: YZ125K Rebuild
Post by: 80-85 husky on April 03, 2015, 06:18:17 PM
Go Pro Go Pro Go Pro.... rev that sucker ;D
would luurrvve to hear it humming
Title: Re: YZ125K Rebuild
Post by: alexbrown64 on April 03, 2015, 09:22:52 PM
Mainline, i ride with a bumbag that has a mobile phone in it.  That area is only 5 minutes from home....  I remember when i was a kid, i used to go out on my yz80 in the evening and ride until dark.. sometimes running out of petrol in the bush... i would push it home and mum would just look at me and go "alright, have a nice time?"
Husky, i have a Go Pro.  When i get the old girl sorted and find a decent track and get some practice in, i will post up a video of the 125 screaming its head off for a lap...
Cheers,
Alex
Title: Re: YZ125K Rebuild
Post by: mainline on April 03, 2015, 11:17:13 PM
Mainline, i ride with a bumbag that has a mobile phone in it.  That area is only 5 minutes from home....  I remember when i was a kid, i used to go out on my yz80 in the evening and ride until dark.. sometimes running out of petrol in the bush... i would push it home and mum would just look at me and go "alright, have a nice time?"

Funny how things change isn't it .  I used to roll my cr80 down the road till i got to the park then try and ride sedately along the creekline to the bush where we rode. My parents would not have had a clue where i was, who i was with or how i was getting home. These days i am almost ready to attach a.tracking device to my 10 yr old. The world we live in?
Title: Re: YZ125K Rebuild
Post by: alexbrown64 on June 09, 2015, 04:35:44 PM
I have the DLS front brake and Lechien numbers to finish off the tribute bike.  I am also getting a replica Yamaha jersey from the era to go with it.  Almost done....  a few more rides needed to iron out the bugs......

But!, i am a glutten for punishment and have another project under way with its brother, the Oz version.  I am doing this one on the cheap, to be used as a practice bike and bush hack... but it is still costing a bit.  I painted the frame myself using epoxy enamel but i am going to take it to the powder coaters for a more durable finish.
I am on the lookout for a good condition original exhaust pipe if any one has one.  At great expense, i purchased a pipe from the US and on closer inspection it is for an 84 L model.  They look very close and would fit OK, but it niggles me.

(https://ffd8mq-bn1305.files.1drv.com/y4mtwgsn87S9AyjXOxJ4oSWR5xM_SAVKOmBA9hwSvlWBS6HIa2yC3mCDOZtj8kNUnI80ZaT8sWdhoirzA3FndffUc0BruxssxAqLVnFkiBfNyxEQQOVHQETJFC1MUTcm8uDJHqcu4ZOMvhRrQHcQie8EtUQYr_-jKk_MNXe_n_BQ2kR4oZrqTxnLVItOCo3PloQQdS39Zdhb3M62SptzC_mMQ?width=660&height=495&cropmode=none)

Cheers,
Alex
Title: Re: YZ125K Rebuild
Post by: Ekka on June 09, 2015, 07:18:07 PM
Looks like the bug has bitten you good  ;)
Title: Re: YZ125K Rebuild
Post by: Billet YZ on June 09, 2015, 10:27:44 PM
YZ 125 K & YZ 125 L  share the same part number for the exhaust.
Title: Re: YZ125K Rebuild
Post by: alexbrown64 on June 09, 2015, 11:57:01 PM
Its a big bug Ekka... just gotta get out and ride more but it is so hard these days... barely a riding spot open in WA anymore.
Billet, the part numbers for K and L are:

EXHAUST PIPE ASSEMBLY
39W-14610-00-00
$296.99
PART OBSOLETE

EXHAUST PIPE ASSEMBLY LASSEMBLY
24X-14610-00-00
$309.99
PART OBSOLETE

They are interchangeable and look very similar, but the L is slightly narrower.  The K muffler is non repackable and the L muffler has rivets and is repackable.  I have the L muffler and will keep that as i can repack it as neccessary.
Title: Re: YZ125K Rebuild
Post by: alexbrown64 on June 11, 2015, 04:58:02 PM
The bike is almost there... i fitted the DLS to the race bike and it works well (in the shed).  These brake plates are hard to get and expensive.  It came on the old OZ model K i just bought.  I whipped it off, cleaned it up, adjusted it and fitted it without too much trouble.  I grabbed some adjustment instructions from various forums and have added them to my website.  The DLS for the 38mm forks is different than for most other models.  The lug that slips into the fork leg is only at 1 o'clock on the 38mm model as opposed to 3 o'clock on larger forks.
(https://4dsqga-bn1305.files.1drv.com/y4mFUis1GKxkF-z1_609KbD2LX-_sksHfKti_-9s5KMeDU-oa_7avk3WIdLNjXsYMp4NJryb_gELGJKk-GBgqqmGiPQHMvDvpjgPSbdAFt5UtmBsMomkNIKiZhFEjG3rsTh3SBgemq61AvTDYD34IUKNj6d4YKN3XnNB1Hk1JRyHGp8jVKvikc4G5ZKniHv8sretkqHXd00aWGjMFBWkGn0lA?width=660&height=495&cropmode=none)

Cheers,
Alex
Title: Re: YZ125K Rebuild
Post by: tony27 on June 11, 2015, 09:38:08 PM
Same plate as fitted to the G & H model 465s & H model 250s, have a later model plate sitting in the garage that I robbed parts off for my 465
Title: Re: YZ125K Rebuild
Post by: alexbrown64 on June 11, 2015, 09:59:18 PM
Yes, i just read the YZ125L magazine report and the 43mm forks on that had the 1 o'clock insert.  Most plates i see for sale though have the 3 o'clock insert and they are all heading up over $2-300 US now.  Some DLS plates only have the steel arms too...
Title: Re: YZ125K Rebuild
Post by: micko on June 25, 2015, 06:59:30 PM
Alex, you should come riding with us on Saturday @ducksnuts mx park. (check it out on the web) Would be great track for your bike.
Micko
Title: Re: YZ125K Rebuild
Post by: alexbrown64 on June 25, 2015, 08:29:29 PM
I would love to go for a ride and meet some of you Saturday Micko, ... but i am still away on the Wheatstone platform.  I looked up the ducks nuts park and it looks brilliant.  Thats the sort of thing i'm looking for.  Will definitely get there soon i hope.  And your right, the 125 would scream on those tracks.  If you get there, please post up some pics of the day.
Cheers,
Alex
Title: Re: YZ125K Rebuild
Post by: SimonC on June 25, 2015, 08:53:23 PM
If you are north of the river I can recommend the Pinjar Off Road Area - remarkably good little facility if you go midweek, a few different trails to ride on, and it's free and you don't have to pay anything to Motorcycling Australia for the privilege of riding your own bike. Don't go near it at a weekend though.
Title: Re: YZ125K Rebuild
Post by: micko on June 26, 2015, 06:54:07 PM
No worries Alex, will get some pics and go pro footage. Cheers Micko
Title: Re: YZ125K Rebuild
Post by: alexbrown64 on June 26, 2015, 08:29:09 PM
SimonC, i might take a run up to Pinjar to test the bike out at some stage.  Someone was saying they have closed a lot of it due to development.
Should start a thread up with pics on riding areas around the Perth area.
Cheers,
Alex
Title: Re: YZ125K Rebuild
Post by: SimonC on June 26, 2015, 11:13:50 PM
Whole thing is currently closed due to forestry operations, I think back to normal in July. Good place to test your suspension out.
Title: Re: YZ125K Rebuild
Post by: alexbrown64 on July 08, 2015, 12:22:03 AM
I rebuilt the OZ version wheels and installed them on the bike.  This took some time and effort, so i made a tutorial up on how to relace conical hubs, and posted it up in the tech section.
I have used the original rims but powdercoated them black.  It was going to cost $200 to re-anodize, or $400 for new rims. The powdercoaters blasted and painted them for $10 each.  I also had the hubs done for the same price and got the frame done at the same time.
The zinc on the original spokes was worn out so i have put those away for later electroplating.  I also broke one removing it, but one of the guys on here is hopefully sending me one to replace it.  I located a front and rear OEM set from Tamor Trading.  Tony did me a good deal and he express posted them to me.  I got everything back and relaced them.  I cleaned, inspected and repacked the bearings then polished up all the bolts, adjusters and axle.  There is also another 50T alloy sprocket on there so that i can easily swap wheels over with the other 125K.
Cheers,
(https://ctcteg-bn1305.files.1drv.com/y4mah__05WVeNTwiw7JR7oY8GfS7XGc2qV3iCLvyDVt75VdIakyxPboGBvvIDISuY01g3rBTSlFYcYZdnbHaVmcPdbVDsjsGwNcgLATsu8nAWU6UAUYVu74xQQaWu3GPsp6EBVRppYySoml461NXDh6cEJMk_7h8LYEwQdTHOCT2aDfSiJtLGg8rx828_9RBBkFc8cxSN6i72NIKRf3JxzDJQ?width=660&height=495&cropmode=none)
Title: Re: YZ125K Rebuild
Post by: Tomas on September 26, 2015, 02:13:14 PM
Like your enthusiasm Alex. Thought I have too many spares having a spare set of engine cases and set of gears for my RM. Good work  :)
Title: Re: YZ125K Rebuild
Post by: Lozza on September 26, 2015, 04:37:28 PM
Woodruff key isn't essential flywheel will stay put without it. Few more pics of the gear lever please  :D
Title: Re: YZ125K Rebuild
Post by: alexbrown64 on September 27, 2015, 11:36:39 AM
The gearshift was sent to the scrap yard to be sent to China to be made into Chinese pit bikes.  I thought about whacking the rotor in without the key, just like my PVL, but i found one, so in it went.  I think i have to many spares now Tomas.  May be giving some of the L cases away if any one wants some.. just pay for postage.
Well, feeling good as West Coast kicked butt last night, i headed to the shed this morning before the kids woke up and had a bit of a go at the bike.  I got all my seals fitted to the clutch cover.  The water pump seal, i pressed in with a G clamp.  I have a new power valve linkage, but i only use it to compare wear against my old ones.  The used one in this case was OK, so i re-fitted it.  This cover was now ready to fit.

It was now time to fit the engine.  All went well and it slipped straight in.  This is when you adjust the clutch.  Loosen the nut in the centre of the clutch hub and wind out the rod slightly.  Then adjust your cable so that the clutch arm that comes out of the case on the right side aligns with the small mark on the case.  Then wind the clutch rod back in until it touches and do the lock nut back up.  We are now ready to fit the clutch cover.

To fit the cover, as explained earlier when i refitted the Lechien one, you have to fit the governor in the clutch cover first.  I picked up my governor and realized the spring was floppy.  My spare governor (from an L) had a helical gear but had a tight spring.  Using pics and diagrams, i rebuilt one good governor and the spring felt perfect.  The previous owner must of had it apart and left a few spacers out.

Fit the governor in the clutch cover with the power valve plate going into the groove in the governor.  Have your dowels and gasket on, the gently work the cover onto the engine.  Align the water pump shaft which is on the cover to the white gear on the engine by turning the pump.  Then align the governor into its final position by turning the engine over slowly with the kick start.  The case should just slip on that final 20mm.  I decided to bling the bike by polishing the water pump cover and fitting it together with a red GPI silicon hose.

(https://onmghq-bn1305.files.1drv.com/y4m1PBGLvhzsKZmHfgWnKwBAE2URxI2K8Hi5nOUZhmT8JWNYus0aGJewn4Ao1WybhJ2ECKJGw6GJowtw-lkb6lPuadMelpt96lGGmpWKtttDOROKL03MbY51T2XGIILaqfC2atekow8x_XciChHV8iYQEotuASoGors6UkqJKiA1iw8R7BuBZIXu7MklNiAa9OJ9Xng1KKEpNlvQ_giG4npRQ?width=660&height=495&cropmode=none)

Thats it for now... its time to assembly the ping pong table which looks like it will take more time and has more parts than this bike...

Cheers,
Alex
Title: Re: YZ125K Rebuild
Post by: 80-85 husky on September 27, 2015, 08:21:43 PM
governor? is it a diesel?
Title: Re: YZ125K Rebuild
Post by: alexbrown64 on October 01, 2015, 02:01:07 PM
Not exactly husky, but i got her going this morning and she runs like a scolded cat.  I have a few carb issues, but i gave it shit up the street and she hammered.

(https://pkvidw-bn1305.files.1drv.com/y4mA-7iv8sFthtQ7W0WBV0LJkeH6-Cj-bIK4a3v1AKYrgxvRB20Q3zHuUPDwyhv3-fH2Aik2JL9PILwX9t-uDikbF4CMa3vYF2cx0zQTu61l2_OAW4L26jDkWtPi0UCD6qErwGC9_f3bVndYFbQxXB7m4WS9XQs-yaZE-Y6HnH6zWo7ORXYeyd2nUleBnQJuZ1XceOo2hczgwQQZGYExVlAsg?width=660&height=495&cropmode=none)

Cheers,
Alex
Title: Re: YZ125K Rebuild
Post by: 80-85 husky on October 01, 2015, 05:11:06 PM
Ideal outcome, get that go pro running ;)
Title: Re: YZ125K Rebuild
Post by: alexbrown64 on October 21, 2015, 12:35:06 AM
In the pic above of the Euro K, i had to pinch the pipe and muffler from the Lechien tribute K to get it running.  This is because i only had a 1984 L pipe and muffler.  I have realized that a lot of L parts do not fit the K. I have now found a K pipe and while a little dented, its all original and fits like a glove.  I tried to fit the L muffler as its repackable, but again i was snookered as they don't fit.  I ended up using an old K muffler that i modified...more on that in a minute.  I have also been running the US K with the 58mm cylinder and Wiseco piston.  This has now gone on the white Euro model, so that i could fit the Eric Gorr ported cylinder on the US race bike.  Both  bikes are now almost there.....

OK, before i fitted the cylinders back on, i took some pics to compare standard to modified.  In the pic below, Eric Gorr has resleaved one cylinder back to 56mm and supplied a Wossner piston with it.  He matched up the power valve and cylinder head to suit.  He also did some port work.  I noticed grinding in the intake and exhaust, as well as some new holes added.  Ride report to come, but it will be interesting to compare bikes.

(https://ffdtow-bn1305.files.1drv.com/y4m4u996I6cWpDTpEYQc82Xvk91Q6y_e47tDF0sPc8MseeCMV-dkKJLfiJCgYAyw0ruTI7Jyf2VznSs6EZERBbfOF2TIbv7tLIPBlC0n1ZtqcNNSxbmNJQZhhPXI-47ZPeJEOzS3v5gSBhesASrWiLkyLjARlBI7Hf-Fl6d_Sgi54xGgCoDXLhpVKPnSbuu0ki-72mgZrXhj7QHboOW_cVayg?width=660&height=495&cropmode=none)

Then next pic shows what i had to do to the old K muffler.  At 33 years old, the K packing was knackered but they are a sealed unit.  In 84 they made a slightly different muffler with a replaceable cap.  I had to cut the tip off the K muffler and then cut back about 50mm of outer metal to expose the inner pipe ready to fit the 84 end cap.  I removed all the old packing which was just hard sludge, cleaned everything up, and then fitted new packing.  I fitted the new cap, drilled 4 holes and riveted it on.  Bingo, a K muffler which is now repackable. 

(https://0020xw-bn1305.files.1drv.com/y4maXl6pz0cXuK_WUzBpfthsrb8Ja8rOpXVCsR-bhCY63gxjwIWFvBQMrUK6YMduaxIHWmWQw9Cs4VtNbx3UIFQZnQe1rO-LWPpiKcvhE0lgLmicIOSe0wMQjq6uOjcRrGsi3p-EIDHJBxdSQq9CyFRND8En5Pe-a4mIn479wv3wgIG21CVWCRujkSRP2_njCPKTqkyTBgSh441ymDXnQXRRQ?width=660&height=495&cropmode=none)

The finished product came out well and i have given both the pipe and muffler a coat of 1000F satin black paint.
I still have to swap pipes back as the US race bike gets the Jemco cone pipe and the white K gets mostly stock parts. 

A few other things i have noted.  The white K does not seem to like Iridium plugs. It was a bitch to start with an Iridium plug, then i put an old BR9ES in it and she fired up and run heaps better straight away.
I am having trouble with a decent gear lever.  I bought an aftermarket one that is for this model but it fits like shit.  I have ordered another one for a CRF50 that is supposed to fit.  They are both 11mm shaft and a similar bend, but the Honda one is about 20mm longer.

Cheers,
Alex
Title: Re: YZ125K Rebuild
Post by: alexbrown64 on October 21, 2015, 02:41:48 PM
Put everything together this morning and both bikes stared within 4 kicks.  A few minor idling adjustments and a quick blast around the garden on both.  The US bike is plusher and snappier with a very short power band.  The white K has a broader power spread.  I think the Jemco pipe has a lot to do with it as when it was on the white model, the power felt snappier.
Anyway, both these bad boys are ready for the track and some serious riding... ride reports, pics and go pro vids to come....

(https://pktava-bn1305.files.1drv.com/y4mvRreiDHnSuJrNUK8Ms4imB0kdoVxdEJ5EvWcjIHb3S50-SbNOfTAJW7tVvNzo22KK388NY__VIwWpnubFOw8PNz72CF4hS-oKMTlrohL0OI9V-Y_vM73NNcNDFm0B32O-a7IP6L3sgantlHQ0sM4fv5qzQP0tMD7Nl9_53ZV9YinKp7Cal2E_5iopzU3zoJ3-VamE9wI8YeU0JR0FTH_WQ?width=660&height=495&cropmode=none)

Cheers,

Alex
Title: Re: YZ125K Rebuild
Post by: Rossvickicampbell on October 21, 2015, 04:50:35 PM
Alex - think you might be right re the Jemco pipe.  Tried a YZB one on my bike recently and changed the delivery in much the same way as you mention here - much snappier.
Title: Re: YZ125K Rebuild
Post by: Richo52 on October 21, 2015, 06:01:33 PM
Great looking bikes Alex.......bring them out to the classic MX club here in WA formerly the pre85 club,lot of rides and laid back approach to the rules.........ride and have fun......go as slow or fast as you want.:-)
Title: Re: YZ125K Rebuild
Post by: bishboy on October 21, 2015, 06:46:29 PM
Geez they look good Alex, brings back some memories.  Back in the day I remember painting my frame white and the radiator shrouds red for that worksy look  ::)

Here's few parts for sale if your looking for some more

http://www.gumtree.com.au/s-ad/wollongong-2500/motorcycles/1983-yz125k-parts-vmx-yamaha/1090931978 (http://www.gumtree.com.au/s-ad/wollongong-2500/motorcycles/1983-yz125k-parts-vmx-yamaha/1090931978)
Title: Re: YZ125K Rebuild
Post by: alexbrown64 on October 21, 2015, 07:39:27 PM
Great looking bikes Alex.......bring them out to the classic MX club here in WA formerly the pre85 club,lot of rides and laid back approach to the rules.........ride and have fun......go as slow or fast as you want.:-)
Thats on the cards Richo.  I just have to sort out income protection, MA license, etc.. iron out a few bugs, get fit and i will be there. 

Cheers,
Alex
Title: Re: YZ125K Rebuild
Post by: alexbrown64 on October 21, 2015, 07:44:39 PM
Geez they look good Alex, brings back some memories.  Back in the day I remember painting my frame white and the radiator shrouds red for that worksy look  ::)

Here's few parts for sale if your looking for some more

http://www.gumtree.com.au/s-ad/wollongong-2500/motorcycles/1983-yz125k-parts-vmx-yamaha/1090931978 (http://www.gumtree.com.au/s-ad/wollongong-2500/motorcycles/1983-yz125k-parts-vmx-yamaha/1090931978)
Thanks Bish, i have seen those bits for sale but i think i have everything now.. and two of!!  I cant imagine what a white frame and painted red shrouds would look like..  not sure worksy comes to mind but i used to do all that stuff as well.  Used to make my own fox decals out of contact.. and i took my muffler off my yz80 to give it that "factory" sound  ::)

Cheers,
Alex
Title: Re: YZ125K Rebuild
Post by: Rossvickicampbell on October 21, 2015, 10:11:51 PM
if you wait until you get fit Alex may be a while  ;D
Title: Re: YZ125K Rebuild
Post by: alexbrown64 on October 22, 2015, 12:43:27 AM
if you wait until you get fit Alex may be a while  ;D
Ha! My job keeps me pretty fit but ride fitness is a different thing.  Roscoe, the Jemco pipes definitely pep the bikes up thats for sure...
Title: Re: YZ125K Rebuild
Post by: FourstrokeForever on October 23, 2015, 08:48:51 AM
Nice pair of 125's Alex. they are a credit to your dedication and craftsmanship.

Now you just need to take them out and play with the others. No need to worry about being bike fit. That will come with riding them  :o
Title: Re: YZ125K Rebuild
Post by: alexbrown64 on November 26, 2015, 04:50:49 PM
Both bikes are ready to go... I chose the Euro YZ to take out for its first run.  Loaded it on the bike rack and headed bush. 

(https://001wgw-bn1305.files.1drv.com/y4mU0LXkPsNfdzkociIasCRmqSrgY_VWehtyG_ONYFb5lAU9WoqhzgcMvMViDRtYjTWY6S6UjR7JpbHip4YUmzUAkvSS6L66LRRTdjSp-GZOcY_DatuKEpb213CFyUWnug90frk98WWT2tFHiB0MBzNkMPz47HsK-6UTFtlcnISlooa96AgSQSxzBGUxJTNg41BjUfPYBtYUqrJz4mt7i2qig?width=660&height=495&cropmode=none)

The cylinder on the bike is the one from the US bike, so it was kinda already run in.  Two kicks and i was away and i did some trail bike riding to let everything bed in and sort itself out.  Then it was time to give it some shit..... The two bikes are like chalk and cheese.  I knew this YZ would be the soft version but the difference is huge.  The suspension has all been rebuilt but is all original.  Its soft! In the sand it does not inspire confidence and twitches and wallows.  The US bike with its Race Tech springs, emulators and gold valves is stiffer, plusher and has a more modern feeling.  The engine was crisp when on the boil but 3 or 4 seconds of trail riding and it would take a second to clear its throat and be crisp again.  Perhaps some jetting or just ride it like a 125 and keep it on the gas.  The power is also completely different.  The US bike has the Jemco pipe, PVL ignition and larger carb.  This Euro bike is all standard including original K pipe.  Both have the same gearing but the Euro bike feels slower and goes off the boil very easily requiring more clutch.  I found the US bike had such a short power band that it was like a light switch.... you just twisted the throttle and it was "on".

Overall, i had a good ride and it was nice to do a bit of bush riding again.  The bike ran as expected and sort of feels a little old like me.

What went wrong.  The ride was cut a little short due to the inevitable gremlins after just rebuilding a bike from the ground up.
1. I noticed the wheel seemed to be closer to the right side and the tyre actually rubbed through the fork boot.  Not sure whats going on here... i may have miscalculated when i rebuilt the wheels and just need to pull the rim slightly over to the left.  But also, the axle and fork alignment does not seem quite right.
2. Front brakes are lousy and may need bedding in some more and then some adjusting.
3. I experimented with a CRF50 shifter but it is 15-20mm longer and is a pain on the toe.  Back to the original.
4. I was losing coolant.  Had to add about 150ml.  Its strange because it is acting exactly the same as the US bike.  They both seem to loose fluid through the overflow but bikes are not running hot or steaming.  One has GPI rads and cap and the other is original.  Both have silicon hoses.  I am thinking it is the cheap coolant i am using.  Its the cheap premixed glycol from SuperCheap.  A better coolant may help.\
5. I lost the bolt that holds the right radiator and main exhaust bracket on.  The thread is stripped so will require a Helicoil. I have a kit with all the sizes at home so no problem there.

Thats it for now... i may be taking the US bike out in the morning for its first ride on the Gorr ported cylinder with 56mm Wossner piston.  I have also changed the pilot out for a smaller one as i was getting masses of spooge.  More ride reports to come... and hopefully a GoPro vid.

Cheers,
Alex


Title: Re: YZ125K Rebuild
Post by: Rossvickicampbell on November 26, 2015, 09:34:39 PM
Alex -slightly different note - how do you find the bike rack?  Have fitted one recently to my ute and think it is better than expected so far but haven't had much use.

cheers

Rossco
Title: Re: YZ125K Rebuild
Post by: Paulos on November 26, 2015, 09:39:35 PM
Have you had a look at different needles rather than pilots?
Title: Re: YZ125K Rebuild
Post by: alexbrown64 on November 27, 2015, 01:19:59 AM
Roscoe, the rack is good.  I always use 4 tie downs on the bars just in case.  For one bike its an easy way to take a bike out.  Paulos, i have not looked at different needles... thats a can of worms as it took me ages to work out the 6f4 that i have.  From what i have read, most spooge comes from the pilot being rich.  Anyway, i shall find out tomorrow as i am keen to take the yellow US bike out for its first spin with all its goodies on.

Cheers,
Alex
Title: Re: YZ125K Rebuild
Post by: alexbrown64 on November 27, 2015, 03:07:23 PM
Well, took the US bike out to run it in and what a disaster.  Had a flat front tyre from the word go... no worries, its sandy so i will keep going. Then she nips up once and frees up, then does it again.  I let her cool down and check the plug.  Oily which is good.  I take her out again and in third gear at about 1/3 throttle she seizes up and i have to push her back to the car.
When i first started her up, it only took one kick from cold. It ran clean and crisp and revved well.
New fuel and oil at 25/1.
Bike was running great with old cylinder and piston.
Fitted the new cylinder, Wossner piston, a smaller pilot and replaced the reeds with identical ones.
Bike was running fine in first and second, but when going a little faster and in 3rd/4th she nipped up and released.
Any ideas?

I will strip her down tonight and have a look.  I never checked ring end gap etc.. when i fitted it all up.

I have the options of fitting the old cylinder back on and checking it all out, and once checked out, fitting the new cylinder/piston combo to the Euro bike.

Cheers,

Title: Re: YZ125K Rebuild
Post by: Lozza on November 27, 2015, 07:12:30 PM
Well, took the US bike out to run it in and what a disaster.  Had a flat front tyre from the word go... no worries, its sandy so i will keep going. Then she nips up once and frees up, then does it again.  I let her cool down and check the plug.  Oily which is good.  I take her out again and in third gear at about 1/3 throttle she seizes up and i have to push her back to the car.
When i first started her up, it only took one kick from cold. It ran clean and crisp and revved well.
New fuel and oil at 25/1.
Bike was running great with old cylinder and piston.
Fitted the new cylinder, Wossner piston, a smaller pilot and replaced the reeds with identical ones.
Bike was running fine in first and second, but when going a little faster and in 3rd/4th she nipped up and released.
Any ideas?

I will strip her down tonight and have a look.  I never checked ring end gap etc.. when i fitted it all up.

I have the options of fitting the old cylinder back on and checking it all out, and once checked out, fitting the new cylinder/piston combo to the Euro bike.

Cheers,

There's a hint
Title: Re: YZ125K Rebuild
Post by: alexbrown64 on November 27, 2015, 07:54:41 PM
Thats a big hint Loz... i thought Wossner had a good rep?  Anyway, i pulled it all down and here are the results:

The piston "gripped" on 3 of the 4 corners.  The cylinder seems ok, just some scuffing, but the piston i think is kaput.

My Yamaha manual recommends a ring gap of 0.35-0.5mm.  I checked the end gap several times and i could only manage nearly 10 times less than that at 0.05mm. 

I dont have the gear to accurately measure the piston and bore, but guessing by the ring end gap, i think the tolerances are a bit too close for comfort.  I will drop it all off at the bike shop tomorrow for analysis and repair.

But what is the view on here... my forkup for not checking ring end gap and tolerances, machinist for not checking (Eric Gorr), Wossner, or something else.  I dont think its jetting or oil, dirt, etc..  i think its mechanical as in piston, ring, cylinder...


Cheers,
Alex
Title: Re: YZ125K Rebuild
Post by: Lozza on November 27, 2015, 10:12:48 PM
Looking at your piston its a classic 4 corner seizure, either piston expanded to rapidly, too lean or too hot a plug. If it was another brand I would rule out the piston. A old rule of thumb is 4 thou(0.1mm) per inch of bore for the end gap. On a 56mm bore that is about 10thou or 0.25mm. You can easy measure piston to bore clearance with a feeler guage. Ring end gaps are easy increased. Nothing wrong with that piston is good to go after you file the 4 corners slightly with a points file and a rub over with wet and dry. What was your run in proceedure?

Title: Re: YZ125K Rebuild
Post by: alexbrown64 on November 27, 2015, 10:49:38 PM
Thanks Loz,
My ring end gap was 0.05mm which is 5 times tighter that 0.25mm so maybe that was the problem.  The piston has no heat marks under the crown or any where else.  Bike ran fine with the other cylinder and Wiseco piston.  My run in procedure was to go for a 5-10 minute ride up to 3rd gear and alternate slow to medium revs, then come back and cool it down and go a little harder the next time etc..  I didnt get that far.  I was only 5 minutes of poodling around in first and second, then when i went into third at medium revs she locked up.  TTS as 25/1, standard plug for bike.
Roughly, what size feeler gauge should i get between the cylinder and piston on a 56mm bore?

Cheers,
Alex
Title: Re: YZ125K Rebuild
Post by: sleepy on November 27, 2015, 11:10:51 PM
No piont trying to measure the piston to bore clearance know as the piston will be out of shape.
My gut would tell me that if the ring gap is only .05mm then the bore was probably undersize.
Only time I've seen an issue with a Wossner is when the recomended clearance is ignored either by ignorance or poor workmanship.
Find someone with a micrometer and a bore gauge to measure the bore for you. It should be spot on or a little over the intended bore size. If the piston is for the stock 56mm bore then the bore should be minimum 56.00mm and quite often end up .02 bigger to get the correct clearance.
Can be other causes but first step is to find out what the clearance was and go from there.
Title: Re: YZ125K Rebuild
Post by: Lozza on November 27, 2015, 11:15:40 PM
A 0.05 or 6mm feeler I have had so many of these type dramas with small bore Wossners I refuse to use them. You should be able to see any evidence of the ring ends butting together on the ends themselves and the ring peg. If there is no obvious rub marks it is the piston.
Break in is 5 min up to 1/3 throttle, let cool for 10min 5 min up to 2/3 throttle let cool down go for the doctor, or at a race meeting 2 laps 3/4 pace and slow ride through the pits and then go for the doctor. Never a constant throttle. But that is a piston problem for sure. You should be running a 9.5 or 10 plug in a 125
Title: Re: YZ125K Rebuild
Post by: alexbrown64 on November 27, 2015, 11:49:47 PM
Thanks for the input fella's.  I ducked out to the shed and worked a feeler gauge around the piston from all sides and top and bottom, also rotating the piston etc seeing if there were any high spots.  I could run a 0.05mm feeler all around.  I could just jam my 0.08mm feeler in but it was really tight.
Title: Re: YZ125K Rebuild
Post by: 80-85 husky on November 28, 2015, 08:05:04 AM
over on café husky forum there is a big consensus on Woosners. they require more clearance than the recommended figure. this nip up is typical for a woosy that has been bored to spec. get the hone out and let some more air in.
Title: Re: YZ125K Rebuild
Post by: Lozza on November 28, 2015, 09:59:28 AM
Filing the high spots on the piston is a better idea. Idealy what you need to do is run the engine for a few minutes pull the cylinder and check for high spots on the piston. The problem is much much worse on <50mm pistons
Title: Re: YZ125K Rebuild
Post by: Tomas on November 28, 2015, 10:10:34 AM
Had a couple o cylinders done by Greg Ball when I lived in Sydney an both have clearance around 0.9mm. Actual bore sizes are 55.55 and 56.05. I checked both with bore gage just to know what the cylinder guy did. Never had any issues. Cylinders are runnig wossner pistons.  If you can just push in 0.8 feeler around top of the piston you cylinder is too tight at the bottom (skirt). Take any piston a measure it with a micrometer when you get a chance. You wil be suprised to see where the size of the piston that is printed on the box comes from.
Title: Re: YZ125K Rebuild
Post by: sleepy on November 28, 2015, 11:07:42 AM
Go to your local tool supplier and buy a cheap 50-75mm micrometer and matching telescopic gauge. The feeler gauge method is quite inacurate.
I have bored a lot of cylinders (50+) to suit Wossner pistons and have not seen one nip up, I have had several turn up here that have nipped up after bore jobs from other shops and all have been bored well undersize.
Your ring gap tells a story. The rings that come with Wossners are good quality and if you only have .05 gap when it should be .25 your bore will be undersize by .2/pye which is about .06mm to small. I always measure the pistons and never rely on the size on the box, most measure .02 bigger.
If you get a micrometer and telly gauge send me a PM and I will explain how to use it. 
Title: Re: YZ125K Rebuild
Post by: alexbrown64 on November 28, 2015, 01:28:35 PM
OK, i have decided to take it all in to the bike shop to measure and machine if necessary.  I go away to work tomorrow for a while so cant fuss around too much.  If the ring gap is as precise as Sleepy says, then there is no use in me mucking around.. the piston is probably a bit tight. 
I will however buy some cheap gauges so that in future i can check this sort of stuff out.
Will these gauges be OK for the home handy man to measure the occasional piston and bore...

Also, just for future reference.. if the piston was a whisker tight, can that be honed out or does it need to be bored?

http://www.ebay.com.au/itm/Outside-Micrometer-50-75mm-x-0-01mm-Caliper-Precision-Measuring-for-Workshop-lab-/331711159770?hash=item4d3b869dda:g:fn0AAOxyAs9SOrBr

http://www.ebay.com.au/itm/141535518535?_trksid=p2055119.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT

Cheers,
Alex
Title: Re: YZ125K Rebuild
Post by: alexbrown64 on November 28, 2015, 02:54:22 PM
Just dropped the cylinder etc... of at the bike shop.  He said he has seen it all before. Should be a looser fit because of the steel lined cylinder and forged piston.  Its going to the machine shop to be checked out and worked on. 
Thanks for all the input fella's and i will get back with results and new ride report when i get it all back.

Cheers,
Title: Re: YZ125K Rebuild
Post by: sleepy on November 28, 2015, 04:44:24 PM
Those will do the trick.

Yes the bore can be honed to size. When a cylinder is bored it should be left .003" under the finished size and then honed to final size. 
Title: Re: YZ125K Rebuild
Post by: Lozza on November 28, 2015, 06:06:33 PM
Go to your local tool supplier and buy a cheap 50-75mm micrometer and matching telescopic gauge. The feeler gauge method is quite inacurate.
Telescopic gauge in the hands of 3 different people will give 3 different measurements. I can measure a 0.01mm difference in a bore with feeler gauges, that tells me a measurement(of then clearance) the cylinder bore gauge tells if the cylinder is round and parallel.

http://www.ebay.com.au/itm/Metric-Dial-Bore-Gauge-50-160mm-Cylinder-Internal-Bore-Measuring-Engine-Gage-/161452232262?hash=item25974d8e46:g:ekMAAOSwwbdWPbgZ

Had a couple o cylinders done by Greg Ball when I lived in Sydney an both have clearance around 0.9mm. Actual bore sizes are 55.55 and 56.05. I checked both with bore gage just to know what the cylinder guy did. Never had any issues. Cylinders are runnig wossner pistons.  If you can just push in 0.8 feeler around top of the piston you cylinder is too tight at the bottom (skirt). Take any piston a measure it with a micrometer when you get a chance. You wil be suprised to see where the size of the piston that is printed on the box comes from.

You don't measure the piston at the top, as it has both cam and taper on it. The piston is sized 10mm up from the bottom of the skirt front to back. If you have to run large clearances your giving away free hp.
Title: Re: YZ125K Rebuild
Post by: Tomas on November 28, 2015, 06:12:00 PM
That micrometer is of very good quality. It is Russian made. I have a few of that brand.
Title: Re: YZ125K Rebuild
Post by: alexbrown64 on December 06, 2016, 06:28:08 PM
Its been a long time...

Finally got back to the bike after work, health and other project commitments.  It was honed, piston and ring checked to be in spec, and run in again.  Got the old girl out for a run and it seized again.

I have taken it up to Ray Easson in Perth and he has the cylinder and everything now.  I told him to put a ProX cast piston in and replace the forged Wossner.  He is going fit a new piston and make sure it is all in spec.
He also said it sounds like i have to go up some on the main jet.  So, i will check my settings and go up as far as i can go on the main.

Merry Xmas to everyone and hope you all have a fun filled and accident free holidays...

Cheers,

Title: Re: YZ125K Rebuild
Post by: Lozza on December 06, 2016, 09:31:02 PM
  It was honed, piston and ring checked to be in spec, and run in again.  Got the old girl out for a run and it seized again.

  ....................... put a ProX cast piston in and replace the forged Wossner. 

There endeth your piston drama's, any pics of the piston? If you have lots of vertical lines on the skirt(exhaust side mainly) with the crown in perfect or not even coloured condition you have been affected by the "wossner curse"
Title: Re: YZ125K Rebuild
Post by: evo550 on December 06, 2016, 11:13:33 PM
  It was honed, piston and ring checked to be in spec, and run in again.  Got the old girl out for a run and it seized again.

  ....................... put a ProX cast piston in and replace the forged Wossner. 

There endeth your piston drama's, any pics of the piston? If you have lots of vertical lines on the skirt(exhaust side mainly) with the crown in perfect or not even coloured condition you have been affected by the "wossner curse"
What is this Lozza ? I have a 10 hr Wossner in my sons yz 125 that fits this description...
Title: Re: YZ125K Rebuild
Post by: alexbrown64 on December 07, 2016, 01:01:50 AM
Piston looked like new except for the vertical lines on the 4 sides.  Maybe it was the Wossner curse... anyway, i hope going to a larger main jet and new ProX piston will solve my problem and i can ring the bikes neck without it seizing on me....
Title: Re: YZ125K Rebuild
Post by: Tomas on December 07, 2016, 09:51:03 AM
Had the same issue with Wossner piston on my RM 125. It was not seized but had scoring on piston wher exhaust port is. Just pulled the cylinder after 3 tanks off to see how it looks and notised scoring on piston on exhaust side. Bike is running on ritched side because it is spitting some oil out. Using sintetic Repsol two stroke oil at 25:1. Would this be a bad batch of pistons or is this something that Wossner pistons normally do?
Title: Re: YZ125K Rebuild
Post by: 80-85 husky on December 07, 2016, 01:35:27 PM
woosners known to need 1 - 2 thou more than stated when final honing. std issue on café husky...lots of woosner siezes
Title: Re: YZ125K Rebuild
Post by: skypig on December 07, 2016, 02:53:28 PM
Two things:

1. This thread cost me $18 for a set of the telescoping gauges. (Who knows what quality -$18 delivered!)

2. As I'm sure is mentioned somewhere in the thread: Forged Pistons generally need different (more?) clearance than cast, and sometimes a lot longer to warm up before hard use. Not long enough warm up was blamed for the Wiscos seizing in a Jetski I owned. Maybe BS. But possible due to expansion rates. Cast Pistons seem popular in two strokes, even at the high end. Forged are favored in "Diesels". :)
Title: Re: YZ125K Rebuild
Post by: 80-85 husky on December 07, 2016, 03:15:18 PM
in my experience, oriental bikes used cast pistons and lots of them while euro's used forged at great expense but more life.
eg kdx 250 raced in 84 used two pistons and ring sets for the season. the next year I raced a husky and didn't replace the piston until the end of 86 just a set of rings in late 85. and I didn't  need to bore it, just a new piston.

this comes unstuck if you shag an expensive piston. ol mate on an 84 a/c 250 husky did 3 pistons and rebores in 3 months until we found 1 head bolt bottoming out in the barrel before the head was tight. much unhappiness....
Title: Re: YZ125K Rebuild
Post by: alexbrown64 on December 07, 2016, 10:29:06 PM
Some interesting comments fella's and all taken onboard.  I had a call from Ray Easson and he said he had measured everything up and it was actually a loose fit.  So i was OK on that side of it.  He can't get the ProX from his supplier anymore, so i am going to send him a NOS Yamaha piston kit. 
Now, as stated before, i can run this bike with my other cylinder, Wiseco piston (biggest oversize), and cylinder head, and it will run all day.

I put the new sleeved cylinder on with the Wossner as a loose fit, and it seizes. Ray said its apples and oranges as the two cylinders are different as the new one is ported.
So, my question is, what would be the best way to go to make this new cylinder safe from seizing. I am going to put in a larger main jet, but what about timing.  It has the digital PVL at 1.2mm btdc.  I was thinking of retarding the timing to 1.0mm btdc as Eric Gorr states..

 "Retarding the timing will make the power band smoother in the mid-range and give more top end over rev. When the spark fires closer to TDC, the pressure rise in the cylinder isn't as great. The emphasis is on gaining more degrees of retard at high rpm. This causes a shift of the heat from the cylinder to the pipe. This can prevent the piston from melting at high rpm"

Anyway, thoughts gentlemen?

Cheers
Title: Re: YZ125K Rebuild
Post by: Lozza on December 08, 2016, 11:49:16 AM
woosners known to need 1 - 2 thou more than stated when final honing. std issue on café husky...lots of woosner siezes

Here in lies the problem, when wossner state the clearance should be 0.05mm why the fork would you need to give a piston WAY MORE  clearance Wossner themselves state just so it doesn't seize? Other manufacturers seem to be able to make piston that run perfectly with the clearance they state on the box.

  It was honed, piston and ring checked to be in spec, and run in again.  Got the old girl out for a run and it seized again.

  ....................... put a ProX cast piston in and replace the forged Wossner. 

There endeth your piston drama's, any pics of the piston? If you have lots of vertical lines on the skirt(exhaust side mainly) with the crown in perfect or not even coloured condition you have been affected by the "wossner curse"
What is this Lozza ? I have a 10 hr Wossner in my sons yz 125 that fits this description...

If it had a mild to full seizure the first or every time it gets hot even with rich jetting it's the Wossner Curse'

Had the same issue with Wossner piston on my RM 125. It was not seized but had scoring on piston wher exhaust port is. Just pulled the cylinder after 3 tanks off to see how it looks and notised scoring on piston on exhaust side. Bike is running on ritched side because it is spitting some oil out. Using sintetic Repsol two stroke oil at 25:1. Would this be a bad batch of pistons or is this something that Wossner pistons normally do?

Would seem so
Title: Re: YZ125K Rebuild
Post by: rocketfrog on December 08, 2016, 03:42:05 PM
Is there any known issues with Woosner 250 pistons in Nikasil cylinders that I should know about or is the curse only on the smaller bore sizes? I have never used one but I have one to fit my YZ250D1 (1992) should I refrain and go a OEM or Pro-X cast piston? I have not heard too much good or bad about Woosner but this sounds like a road I dont want to go down with a Nikasil barrel - or at all for that matter!!

For what it is worth, I am tipping that the OEM piston will work fine Alex. I have never had any issue with a stock piston.
Title: Re: YZ125K Rebuild
Post by: alexbrown64 on December 08, 2016, 04:40:01 PM
Thanks fella's... i can pick up an OEM full piston kit for $120 AU delivered.  Thats  bloody good.  Will try that with a few other mods to keep the piston well lubricated and cool and see how we go.

Cheers,

Title: Re: YZ125K Rebuild
Post by: 80-85 husky on December 08, 2016, 07:07:35 PM
quite a few husky 500's have had woosner seizes. a mates 430 did one as well. quite a few run good and I think they may just get a little more honing to assist. they seem to expand a bit more than expected when new.
Title: Re: YZ125K Rebuild
Post by: alexbrown64 on January 05, 2017, 03:18:16 AM
Still waiting on the new OEM piston kit to arrive.  Have also purchased another white fuel tank for the Euro K.  Will be taking the boy out on his RM80N over the next few days, then hope we can both ride together on the my 83 K and his 79 N.

Cheers,

Title: Re: YZ125K Rebuild
Post by: alexbrown64 on January 12, 2017, 06:08:31 PM
Well, that didn't go down well.  Just got my OEM piston kit and what a pile of junk.  Rings were totally missing and the piston pin was so rusty it had gouges in it.  Junk.  I have requested a return.  May go with a new ProX after that experience.

Cheers,

Title: Re: YZ125K Rebuild
Post by: alexbrown64 on January 12, 2017, 06:27:30 PM
Had a look on Ebay, and picked up a brand new ProX piston kit with rings, clips and pin for $113 AU delivered.  Should of went this way the first time around.....

Now its a waiting game to get it, then send it up to Perth to get Ray Easson to fit it up.....

Cheers,
Title: Re: YZ125K Rebuild
Post by: alexbrown64 on March 28, 2017, 04:09:50 PM
Hi guys, just an update.  The boys RM80N is still not running right, so i got him a JR80 to ride in the interim.  He loves it.  Its a 2010 model, and they still use the 1977 5 speed RM80 engine.  Just detuned and with a quiet exhaust.

I took my white YZ125K for a ride with my boy.  He loved hooting around the bush with me.  Only problem was, my clutch went south.  The lever has gone soft and there is something rattling around in the left case where the basket is.  Haven't stripped it down yet, but my guess is adjuster nut has come off or something.

I have the yellow YZ125K cylinder/piston etc back from the shop. Just have to put it all back together. 

I have joined the Classic MXWA club.  Got number 224 which is Ron Lechiens works 125k number.

Cheers,


Title: Re: YZ125K Rebuild
Post by: alexbrown64 on April 05, 2017, 06:01:32 PM
Came back from the gold mines and found time to rip my clutch cover off.  Yep, the big nut had unwound and the basket was barely hanging on.  Not sure how it happened as i thought i had used loktite, torque specs, nibbed washers etc.. but it came loose anyway.

Also, i had left the fuel in the tank while i was working away and guess what happened..

(https://001p1a-bn1305.files.1drv.com/y4m3id03omQ6avKMugUo7RhJQd2d2FDqJM607DEVmdtX-gy1Q8b0XtqwnuY2KLx7NzZFIFQRnzhyWSIL4ea2DIsUiiOSPrpfrY0xY0a1sPpuBNh8fAbpZOrwL83HuTGcuQ6Njl2IuZl441QGj6Hsn4vKsp1MnlxMOJ5J53dt-zjvhjj5eDT1e9s-SEgiTNOSZAkVSv3OnJvpvmaJmClMuNXRQ?width=660&height=660&cropmode=none)

Thats nasty!!

Luckily i did suspect that the tank was going bad, and i found a spare on ShitFace for a hundred dollars.  Looks to be in good condition, but needs a sand and polish and decals.

Well, kids holidays are coming up so i want to get her all back together and running right so i can go for a ride with the boy.

Cheers,

Title: Re: YZ125K Rebuild
Post by: 80-85 husky on April 05, 2017, 06:57:13 PM
all going on there!
Title: Re: YZ125K Rebuild
Post by: Lozza on April 05, 2017, 09:07:03 PM
Clutch lock nut should be nipped up with a rattle gun and fold the lock washer over a flat on the nut.  I don't think anyone ever came up with a solution to stickers not bubbling or unpeeling on a plastic tank. They even did it new IIRC.
Title: Re: YZ125K Rebuild
Post by: alexbrown64 on April 06, 2017, 10:40:03 PM
I didn't use a rattle gun, but i referred to the manual, and torqued the nut up to 58lbs.  I also used a little thread lock and bent the washer over against the nut.  I think this was the original problem, as i did not bend the washer over previously.

Put it all back together and it works like new again.

Next stop was the fuel tank... i replaced the one with the six inch split with the one i got on Facebook.  The replacement started leaking from the petock i put on... cranked that tighter and it fixed that leak... Another leak is coming from a hairline crack next to the mounting brackets.

I looked up YouTube and its an easy fix to plastic weld the polyethylene  to repair the leak.. https://www.youtube.com/watch?v=Lqu3NVqFNCU  I will use my old tank as the donor plastic...

Will do that in the morning.. Will also have to start on the Yellow YZ and put the ProX piston kit and cylinder back in...

Cheers,

Title: Re: YZ125K Rebuild
Post by: ITDOG on April 07, 2017, 10:14:18 PM
try super glue and baking soda...yes it works :P
Title: Re: YZ125K Rebuild
Post by: alexbrown64 on April 23, 2017, 10:05:57 PM
Thanks ITDog.. the original tank was knackered with multiple splits..  The second tank i got had a pin hole leak near the lower mount.  I used a heat gun and some strips of plastic from the original tank and got it fixed.  So far no leaks.

So today i took the white YZ for another blast.  The clutch and tank etc.. all held up well.  I had added some oil to the front forks because they felt soft on an earlier run.  I also had wound up the shock spring and set the sag.  The bike rode really well and felt brilliant through the whoops and sandy corners.
Something wasn't quite right with the engine though.  It ran great at full throttle, but 1/4 to 3/4 it would run rough.  When i pulled up, there was fuel pissing out the carb.  Time to pack up again.

Pulled the carb at home.  Float height perfect at 24mm.  Slightly sticking needle and seat.  I had a Keyster carb kit in the shed so i will swap out the parts.
One other major problem was the carby cap.  It would drop down onto the threads of the carb body about 3/4 of the way and then finally tighter up with only 2 thereads to go.  Obviously something worn out. 
I found another 34mm VM in my parts bin, and it ended up being the body was knackered.  So i swapped it out and now the cap and carb work perfectly together. 

So, next step will be to clean everything up, check the specs and get it all back together. 
Next test run in a few weeks.  Still have to bolt the yellow YZ engine back together.

Just got and email back from Eric Gorr, who ported the cylinder.  I gave him the yellow YZ carb specs and he said it sounds like the main is too lean (280).  He said modern 125's are running up to 400 mains.  He said try a minimum 310, and also richen the needle.  I will get a 360 and 330 (i have a 310) and run it super rich to run it in, and then tune it backwards from there. Hopefully a richer bike and Prox piston and the bike will not nip up next time!!

Cheers,
Title: Re: YZ125K Rebuild
Post by: 80-85 husky on April 24, 2017, 08:09:50 AM
lots of heat cycles to start with on dicky engines 8)
Title: Re: YZ125K Rebuild
Post by: alexbrown64 on April 29, 2017, 07:53:48 PM
Will do Husky.  I'll put a bunch of heat cycles on with the richer jetting.

OK, got to work on the white YZ.  Rebuilt the carb with a different body and lots of new parts and gaskets.  Fitted it up and it runs great.  Sound a lot more crisp that before.

Next problem is the overflow.  The rads seemed to of lost about 200ml from the last ride. I topped it up and after a bit of a warm up, it started coming out the overflow again.
It does this on my yellow YZ as well.

I have the original caps (very old) and a chinese GPI one.  They all say 1.1 bar.  I am thinking new Yamaha OEM cap, and/or get a cap thats 1.6 bar to increase the pressure a whisker.  Anyone had something similar with a fix.

Last but not least, i got hold of another white tank. We shall see how that one is.  I have ordered a new petcock for it.  The whole valve is only 18 delivered for an exact replica of the Yamaha one complete with all gaskets.

Cheers,

Title: Re: YZ125K Rebuild
Post by: alexbrown64 on May 30, 2017, 02:51:27 PM
Finally got to work on the yellow YZ.  Refitted the Eric Gorr ported cylinder with a new ProX piston that was checked and everything cleaned up by Ray Easson.  I changed the jetting.  Main gone from 270 to 310.  Needle gone from second from the top to second from the bottom. Third kick and she burst into life.  Sounds crisp.  I started the white bike at the same time and proceeded to rev them both up in unison and fill the shed up with smoke.  I also fitted my race numbers.  Me and a bud joined the Classic MXWA club, and i asked for 224 just to give the bike the Lechien theme.  Got the new numbers fitted and both bikes are now ready to go riding again.....just gotta run the yellow one in.. lots of heat cycles..

Pic taken in a smoke filled shed.. smells fantastic....
(https://onkhkg-bn1305.files.1drv.com/y4mIsu6BhBSLey8TBUn_6xutvBo1doFMsgNxL38YZb1EOHMWwOZG6RpwLw-11ZzYeuvk9wy2FqElXNUttQ8lhM9sZkDM_rOXms8BXU7R32patBWWQocLvd2w3rZJy21xSKVoDZNmRg4qTQfCPy8kPHo7DBvoy6msgwQ3Dlgl_PPa3aNtRSfqRGqCqpeO5Fy0M92DrWVqizj_f_VwlapK3N6_Q?width=660&height=371&cropmode=none)

Cheers,

 
Title: Re: YZ125K Rebuild
Post by: 80-85 husky on May 30, 2017, 05:07:15 PM
using castor 927 I hope 8)
Title: Re: YZ125K Rebuild
Post by: alexbrown64 on May 30, 2017, 05:43:33 PM
I should change to that perfume, but i am running good old Castrol TTS
Title: Re: YZ125K Rebuild
Post by: 80-85 husky on May 30, 2017, 06:03:24 PM
the only better thing than running the castor is the bike in front running castor... ;D
Title: Re: YZ125K Rebuild
Post by: alexbrown64 on July 11, 2017, 12:18:27 AM
I've been hit by the greed of photobucket. Never fear, I have downloaded all my pics and reuploaded them to my one drive. I will be updating and rebuilding this thread..will just take a while.
Cheers,
Alex
Title: Re: YZ125K Rebuild
Post by: alexbrown64 on October 13, 2017, 11:33:56 PM
Finally got a chance to update the K page. With 20,000 views, i think a few people were interested in seeing the pics updated.
I have taken both K's out a few times now... and everytime i have been plagued with minor and major hassles.  Went to ducks nuts ride park a month ago.  Even though i was taking it easy, both bikes blew head gaskets. I fitted new oem cylinder studs, nuts washers and head gasket.
Today i had a ride with a mate and siezed the US model again.  This is after a new ProX piston fitted and checked by Ray Easson and given the OK.  Also rejetted for extra rich. 

(https://v0ezpw-bn1305.files.1drv.com/y4m0qDX9kMxphjGfI-l5EKfzkSLaJzGZk0eStlvVteUXWgXZnNhb_RSXh0F8CQsIAzv4q5jFvnPzeF9PYXaCvrTksjf2E14djEOuEtPqJv110orhX5nl6mTqT99lqUUnVu08ERXWp9C0cbFcVfQGCFywRUUK2ONyxu_H2XqPY7RnszxO86ORPAGAtEX3PbHZ40uXNFUJqT-DHFJr9zBiJwLGw?width=660&height=371&cropmode=none)

(https://js1cyg-bn1305.files.1drv.com/y4mCxOw51yJXU6Iq9Pv5pOSaTqScQVtMFePzmYxoIZetDfV3Ux4OrDfCRS9ccEUEVh_6JEfWhbrQu1jtHqPbO_Z1z4zjlBscfuOScnkbRB25lvqEvvImb4-CLlk1gp6mMnHfiD5E5AyBYcSE5k3OJ3k9QKQwLDNV5jzLCuEEVFF2CFvyq0y-qLUGtwK9g2_S-pX4WMPr0dBze2_tQ3sggXkMw?width=660&height=440&cropmode=none)

Cant explain whats going on with the cylinder.  I can run the other cylinder on the US bike and thrash it, and its fine. But put the ported one on, and it plays up.  I am going to have to swap parts on bikes to try and track down the problem.

On another note, i may be picking up a third K in the morning. This could get interesting.....

Cheers,

Title: Re: YZ125K Rebuild
Post by: alexbrown64 on October 16, 2017, 03:58:53 PM
Didnt pick up the 3rd K. It was a piece of shit.

As reported, i seized the yellow bike again.  Bike seemed to run fine with the richer jetting, but seemed to get a bit spluttery until i revved it up to clear its throat. It also felt slower than before.

Ripped the cylinder off the K and what a mess.  It has the 4 point seizure, but also the aluminium at the front was melted. The ring was fine.  I cleaned the aluminium off the cylinder and there is no scoring. In fact, the hone marks are all still there.

There are no overheating marks under the piston.
I had jetted extra rich. The plug looks Ok. Not dark, but not white.  Kinda light grey. Bike is still spooging.
Bike would run fine at 3/4 power, but nipped up under a few minutes of full power.
All gaskets Oem and new.

(https://vkezpw-bn1305.files.1drv.com/y4mZsBAjdpQInQT-uOMxAa6_oIng2aXeFPqnSJ_8XdPrVCct9Ir1CmZMXXrFJQeD1p-Nxh2viR9tZpccA1jPpfnlt8FLB3dIfEXcKhrdwCJf1-ySsJenIokLnTmf9t9wjZ3pY-UsVk3-mWaZ6VwL_-qjWTE2P8WvMkJCK8oepIWeKFZv-OfXoVPIZku_-pXhrB2aYYqeAFmCVOdFWiubCL6pg?width=660&height=371&cropmode=none)

(https://teezpw-bn1305.files.1drv.com/y4m-EBwf05lphy92-SQv5ndXxJUl1mKtntjSF_9Qjrr5PeiLPxQ03PcLqm4jvP3xdLOInWbaeXGROF3Z2fKHDHFIvAIXxZb6jVVIbX_xC_O2bAin-sxU1DOtDdZpfGnF8vAA1fhW8YzAz4m_UrE7JwGxyV4s6CRcG-5kj2rfA63rBWkpRATvJ5q_EQvKMBiOdW3N__IBvpGlnw-SUC62i2Nkg?width=660&height=371&cropmode=none)

(https://vufpmg-bn1305.files.1drv.com/y4msEYUKZjCC9lhBd3Bh3GhEVuVe46EbSBHMuvvsxd0qq94_Ks1jjzrhPc0-xXEBCJCZmeLYLr6-vCpgPhseqGqiMdexkVWU4UZJMx44f1dGVONVRys-rxdxY6pOm9IiNbo33uiIuciFF-v04MxUJgqIVOHMxOJUDx01yPdEQlwLpSF3rGF8PuuFjUKkWyVhGcEqjUdEL3h3IHMAzLf5Qg8RA?width=660&height=371&cropmode=none)

Just want some advice on what to do next. This is the second piston, and multiple siezures. 
Bike seems to run fine when i put my other cylinder on with the 58mm oversize Wiseco piston.

I cleaned the cylinder with acid and there are no gouges or marks... it was just melted alloy and all the hone marks are still there.  Can i hone again and use another new piston? or is it rebore  time? I dont care about a loss of performance at the moment.  I would rather not keep reboring if possible until i sort this mess out. I can get another standard size prox piston if necessary.

Should i get rid of the 36mm oversize carb and go back to the standard carb and jetting?

Should i run this ported cylinder in my other standard bike to see if it reacts differently?

Should i run the white bikes cylinder with Wiseco piston in my yellow bike and see if that still runs fine? as it used to work great.

Any other things i can do? I emailed Eric Gorr again as he did the cylinder originally. Before i ran it this time, he had recommended the 310 main jet, which i installed.

Title: Re: YZ125K Rebuild
Post by: 80-85 husky on October 16, 2017, 08:54:52 PM
serious seizure....back to basics...air leaks? base, case and seals ok?
Title: Re: YZ125K Rebuild
Post by: Lozza on October 16, 2017, 09:47:11 PM
What heat range plug? Have you a pic of the piston crown? Looks slightly lean to me. Do you ride on sandy tracks (I assume that being from WA)?
Title: Re: YZ125K Rebuild
Post by: alexbrown64 on October 16, 2017, 11:02:17 PM
It using the standard B9EV range plug.

Bike did not exhibit any sign of air leak.  No hunting, no running rough etc. Started second kick and idled perfectly.
I did less than an hour on the piston. I can take a pic if you like of the crown.  Bike shop said it looked like some detonation.
Does look a bit lean, but plug wasnt white.  It was grey and bike was still spooging.  I just checked the MXA report for 83 and they recommend 280 main on the 36mm carb. I was running 310.
I had inspected the piston when i ran it in, before i opened it right up, and it did show signs of scoring on the 4 corners at 45 minutes of gentle running in time.

I may get a new piston kit, and run the cylinder in my stock K.  Gently run it in and check the corners again.

I will also run my stock cylinder in the modified bike again and see if it exhibits abnormal signs.

I will also make a leak tester to check both bikes for air leaks.

I am a little stumped...

Cheers,
Title: Re: YZ125K Rebuild
Post by: Tomas on October 16, 2017, 11:20:00 PM
I would say that you may want to go next size up on needle jet and also pull needle up a notch. Swaping only main jet may not help as needle jet may restrict fuel flow and that will lean fuel mixture. When you go up on main jet you also have to adjust everything else. Worked for me. Also I would go through at least a couple of tanks of fuel before going a full throttle. Check Mikuni web site. There is a chart that explains how needle, main jet, jet needle etc affects fuel mixture depending on in which position your throttle is. Also I would go back to stock carburetor. These bikes are already tuned to higher power output from factory
Title: Re: YZ125K Rebuild
Post by: 80-85 husky on October 17, 2017, 07:34:54 AM
needle jet seize sounds like its on the money if the bike is airtitght. oil spooge tells you that you "didnt" forget the to mix the oil.. ::)
Title: Re: YZ125K Rebuild
Post by: Lozza on October 17, 2017, 11:50:02 AM
It using the standard B9EV range plug.

Bike did not exhibit any sign of air leak.  No hunting, no running rough etc. Started second kick and idled perfectly.
I did less than an hour on the piston. I can take a pic if you like of the crown.  Bike shop said it looked like some detonation.
Does look a bit lean, but plug wasnt white.  It was grey and bike was still spooging.  I just checked the MXA report for 83 and they recommend 280 main on the 36mm carb. I was running 310.
I had inspected the piston when i ran it in, before i opened it right up, and it did show signs of scoring on the 4 corners at 45 minutes of gentle running in time.

I may get a new piston kit, and run the cylinder in my stock K.  Gently run it in and check the corners again.

I will also run my stock cylinder in the modified bike again and see if it exhibits abnormal signs.

I will also make a leak tester to check both bikes for air leaks.

I am a little stumped...

Cheers,

The is a LOT of deto there. A 9 is to hot in a 125, in a modern well cooled 250 we run 9.5's a 10 or 10.5 in hot weather or sandy tracks is more like it. You should never be gentle running in, let it idle for 10-15 min then go for it.
I would after running in pull the cylinder and look for high spots (polished areas on the piston) then hit those areas with 600 wet and dry and the a green scour pad all over the piston. Rinse repeat. I would also look closely at the top edge of the exhaust port window to see if that is finished correctly.
Title: Re: YZ125K Rebuild
Post by: rocketfrog on October 17, 2017, 11:50:34 AM
Wouldn't the spooge be a sign of over fuelling? Perhaps you are literally washing the bore with fuel. Oil should cling to the cylinder wall in order to transfer the heat and provide a bearing surface.

 I would reset to stock carb and jetting and a new piston, go through the std run in procedure and then tear down the top end and inspect the piston and the cylinder for high spots for signs of metal transfer, localised heating etc, and correct as necessary.

Kawasaki recommend the piston is run to break in (15 mins of low throttle running) and then tear down the top end and carefully rub down the high spots on the piston if there are any - True this is a Kawasaki procedure recommended for electrofusion bores but I cant see how it couldn't help and save you roaching pistons. Besides, you must have this top end off job down to F1 pit stop standards by now Alex, what is a few minutes work for the peace of mind?

You should not be having this much drama, don't overthink it - go back to basics. Basically what Tomas and Lozza are saying would be my 2 cents on the topic.
Title: Re: YZ125K Rebuild
Post by: justanothercgrader on October 17, 2017, 08:00:58 PM
The sponge could be a sign of richness at other throttle openings,
You need to go back to some "base settings"

i would install a stock type cast piston, and Check the squish distance,

 install the stock carb and jetting, maybe raise the needle and up a main size or two.

if i remember you have a funky ignition?, If so why not install the original ignition, or at least you must check the settings.

Another thought is that the cooling system, pump, is actually pumping, you say there is overflow, or is it overheating because there is no flow?

As they all say air leak test to be 100%

I feel for you….
Title: Re: YZ125K Rebuild
Post by: alexbrown64 on October 17, 2017, 09:12:13 PM
Thanks for the input fella's.
Yep, it shouldn't be this hard, but i am not a tuning whizz and the bike had so many mods at once, that its hard to know whats going on.

I am getting the gear together to make my own leak tester for the K.  I will run a leak down test. That will eliminate, or show up that problem.

I am ordering a new Prox cast piston kit.  Bore still looks like new in the cylinder. Will check the squish and compression psi numbers.

I am assembling the engine, but removing it from the bike and taking it up to Ray Easson Motorcycles.  He wants to run some compression ratio checks and measure everything up.  He can machine the head etc to modify squish if necessary.

I got a message from Harry Klemm who is quite a tuner, and he says their is a lot of detonation there and to run race fuel.  I dont want to go down the race fuel track, and would rather detune the engine to go back to a regular octane fuel.  Hopefully by timing and head mods. 

I may go down the track of getting a new Mikuni 34mm carb with stock jetting.  Also add my stock exhaust and stock ignition.  Then, using the advice from you guys, run it in and keep checking the piston.  Sand any high spots.  Hopefully jet to get it nice, and then start adding my trick parts back and checking the piston and plug regularly.  Could also change the heat range of the plug as suggested. I may change my brand of oil and go to a different ratio.  Maxima at 32/1 or something like that.

Lots of options open, and again its going to take some time to go through all this...

Cheers,

Title: Re: YZ125K Rebuild
Post by: Lozza on October 17, 2017, 10:21:36 PM
Have you run a timing light on the engine while running?
Title: Re: YZ125K Rebuild
Post by: alexbrown64 on October 17, 2017, 10:50:45 PM
No Lozza. Never done that and not sure how.  I always set the timing using the tdc method and a dial gauge.
Can you show me some pics of how to do it and what parts i need.  I will also do that check.
Cheers,
Title: Re: YZ125K Rebuild
Post by: justanothercgrader on October 18, 2017, 03:58:05 PM
TTS is a good oil may not be the best, but most older bikes run that in the "olden day's"
I know you said the other bike runs good, but what fuel are you actually using?
Also, this suggestion of sanding the high spots on the piston sounds extreme, i would be checking the cylinder for roundness instead.

Way back, we used to slap a new piston and ring, super fuel, Castrol TT, warm the bike up, cool it down at home, do 1/2 dozen slow laps, cool it down, then go out and rip the shit out off it,

I am weary of your ignition, not the quality, rather the set up???
Title: Re: YZ125K Rebuild
Post by: Lozza on October 18, 2017, 05:14:10 PM
No Lozza. Never done that and not sure how.  I always set the timing using the tdc method and a dial gauge.
Can you show me some pics of how to do it and what parts i need.  I will also do that check.
Cheers,

If you bought an aftermarket ignition, it must have supplied a curve ie @4000rpm ignition timing is 20*
So you would have to make a mark on the flywheel at 20* BTDC against a reference mark on the stator. Then strobe with a timing light and adjust the stator to suit. Just need the dial gauge the torqsoft website, a copy of the ignition curve and a timing light.

Also, this suggestion of sanding the high spots on the piston sounds extreme, i would be checking the cylinder for roundness instead.

The piston is checks the cylinder for roundness ......when hot.
Title: Re: YZ125K Rebuild
Post by: OverTheHill on October 19, 2017, 01:00:01 PM
No Lozza. Never done that and not sure how.  I always set the timing using the tdc method and a dial gauge.
Can you show me some pics of how to do it and what parts i need.  I will also do that check.
Cheers,

If you bought an aftermarket ignition, it must have supplied a curve ie @4000rpm ignition timing is 20*
So you would have to make a mark on the flywheel at 20* BTDC against a reference mark on the stator. Then strobe with a timing light and adjust the stator to suit. Just need the dial gauge the torqsoft website, a copy of the ignition curve and a timing light.

Also, this suggestion of sanding the high spots on the piston sounds extreme, i would be checking the cylinder for roundness instead.

The piston is checks the cylinder for roundness ......when hot.
Lozza, not sure if i'm having a bad day [what day is it]. Should the mark [you make] on the flywheel say 20 degrees, be lined up with another mark you'll make on say the case or something 'unmovable' so if it's firing away from there you can move the stator to bring the marks inline. If marks are made on the stator [talking strobe marks not factory marks] they'll move around together when strobing & stay apart if are strobing out of line in the first place that is. I'll shut up--i'm having a bad day. 3 days of 'school built' mini bikes racing does that. [close to 200 bikes & 110cc sidecars plus 70cc honda clone motards] Just about pulled me bloody shoulder out trying to start the single speed 50's 2 strokes [cheapy chinese motors] on the start line, can of either start ya bastard in one hand & a bucket to pick up everything that fell off at the start line, nut bolts footrests, mufflers, chains [& riders]. Anyway--!! forgotten the subject.
Title: Re: YZ125K Rebuild
Post by: Lozza on October 19, 2017, 01:11:00 PM
It really doesn't matter where the reference mark is because you normally make a TDC mark on the flywheel so stator or reference mark/rotor marks line up at TDC. Then make another mark(s) XX* BTDC on the rotor. So you have 4 marks cases stator and 2 (or more) on the rotor. Move the stotor to adjust the timing against stator or case marks
Title: Re: YZ125K Rebuild
Post by: OverTheHill on October 19, 2017, 02:21:07 PM
Ok, thanks for that. Had a 125k back in the day, damn good model too. Hadn't even looked at the heading [125k] so no doubt would be rotor not flywheel, if original.
Title: Re: YZ125K Rebuild
Post by: Tomas on October 19, 2017, 03:17:51 PM
do not know much about ignitions but I have used Horse Powe Ignition of Belgium(I belive) CDI unit on my80 RM 125(They only offer cdi unit for 81 but i thought that they are more or less the same)  and it works well. It is mixed up with original suzuki rotor and stator that was rewinded by a local elecrician and set to what manual recomends. Ignition coil is an e-bay job for $25 delivered(made in china I guess).  I reckon you will probably be beter of  with stock ignition that can be set to what was tested by maufacturer and worked well. Only thing I would recomend to replace by a new unit is CDI(even nos CDI unit can be 30+years old and may not last). Most of new units for these bikes are just copies of original unit but they are brand new. Ported cylinder should not be an issue. Run it in for longer and it should be fine. I run Repsol 2t offroad oil at 20:1 and see hardly any blue smoke when running at full throttle. It is running on ritcher/safer side just in case. This is what manufacturer recomended for a new bike. Dont worry about all tat dribble about how good modern oils are and you can run mix at 100 to 1. Cheaper to run at 20 to 1 than keep buying new pistons.
Also check your cylinder for roundnes if you can. Newly bored 2stroke cylinder can have high spots since there is a lots of holes(ports) and these high spots will grow when motor is hot.  It takes lot of skill to hone cylinder and get it round and straight. Thats why you should run your cylinder in for a little longer. Even modern cars should not be driven hard for first 1500 or so km i was told :)
Title: Re: YZ125K Rebuild
Post by: alexbrown64 on October 19, 2017, 03:34:24 PM
Ok, so let me get this straight.
I set the bike to tdc
I use a dial gauge to make a mark on my rotor and stator at, for example 20 degrees btdc.
I then strobe the bike to see if the marks align at a certain given rpm that would be given by pvl for this ignition.

Make adjustments as nesessary.

Does that sound correct.

Questions:
Do I need a 2 T timing light.
What rpm gauge is used.
Is there an all in one unit that is cheap.
Do you just download and print out a dial gauge.
What's the software for.

Justanothercgrader why are you weary of my setup? I did it as per pvl instructions. I do think the timing light is a great idea to check the advance though.

Tomas, bike shop did test for round, but will do again.

Great input everyone

Title: Re: YZ125K Rebuild
Post by: Tomas on October 19, 2017, 07:37:06 PM
Would not be easier to use ignition on your stock bike as a reference to set your PVL ignition. All you need to get right is when the magnet in rotor pases coil core that is bolted to stator . Use dial clock and maybe timing wheel($10-15) to harvest these values and use them to set your PVL. So you have PVL ignition set to stock yamahaha setting :)
Title: Re: YZ125K Rebuild
Post by: Lozza on October 20, 2017, 11:14:54 PM
Would not be easier to use ignition on your stock bike as a reference to set your PVL ignition. All you need to get right is when the magnet in rotor pases coil core that is bolted to stator . Use dial clock and maybe timing wheel($10-15) to harvest these values and use them to set your PVL. So you have PVL ignition set to stock yamahaha setting :)
might not be possible and you would have no use for the PVL.


Yes you are almost there. Just use dial gauge to give you mm BTDC that corresponds to the amount of advance. Distance from tdc is more accurate than a degree wheel.
http://www.torqsoft.net/piston-position.html
http://www.ebay.com.au/itm/152070562497
here is a cheap and cheerful tacho.
A cheap timing light is OK that will do 2T and 4T, there are more expensive lights that can tell you the amount of advance/rpm most will only go up to 5000 rpm on 2T mode.
You will have either of the top 2 curves
(https://farm6.staticflickr.com/5557/14873999166_56ff544b82_o.jpg)
Title: Re: YZ125K Rebuild
Post by: Tomas on October 21, 2017, 01:11:33 AM
And why it might not be possible?
Would you like to explain.
Anything special about PVL ignitions? Dont they use magnets and coils like all other ignitions?


Title: Re: YZ125K Rebuild
Post by: alexbrown64 on October 21, 2017, 11:54:16 PM
Would not be easier to use ignition on your stock bike as a reference to set your PVL ignition. All you need to get right is when the magnet in rotor pases coil core that is bolted to stator . Use dial clock and maybe timing wheel($10-15) to harvest these values and use them to set your PVL. So you have PVL ignition set to stock yamahaha setting :)

Hi Tomas, I know you set the stock unit for 1.88mm btdc and align the rotor to the stator.  The rotor has a keyway so it is fixed.
The PVL has no keyway. For my bike and pvl, you set the piston to 1.2 btdc and put the rotor on to roughly align the marks then adjust the stator to get them perfectly aligned. The PVL and stock Yamaha use different timing settings.  In fact, I went back to the instructions and it said I should be using between 1-1.2mm, so even to start with I could be 20% too advanced (1mm compared to 1.2mm), and it said you may have to even retard more for modified engines.  So maybe it should be .8mm.  The stock Yamaha setting would probably be way to advanced for the PVL ignition.

I found out my stroke is 50mm
My rod is 98mm centre to centre

When I use the torque soft app at 20* I get a value of 1.88mm

I have the Digital PVL, not an analogue one, and an internal rotor.  Not sure about windings etc.. I dont know my pvl cdi number yet, as I am working away. So, not sure what PVL ignition curve I have.  Would the curve not be closest to the curve on the bottom right?

My Yamaha curve in my manual shows about 26* btdc  at 4000 rpm

When I find out the correct value from pvl and then plug it into torqsoft, I assume I set the piston with my dial gauge at the given mm btdc, then make a mark on my outer stator and inner rotor that can be anywhere, but they must align.  Then start the bike and using the rpm gauge and timing light, bring the rpm to the correct range and check to see if the marks line up, and then adjust the stator a whisker to align the marks.  Does that process now sound correct?

Would this just test whether the ignition was working properly and set it to the recommended PVL baseline?  As even PVL states that the measurements they give are only a starting point.  I may need to go a lot more retarded for a higher compression engine no?
Also have to look at a leakdown test, a compression test, compression ratio test (Yamaha state 7.8-9.9:1) and squish band test. Yamaha recommends the squish for this bike at .8mm.  Does anyone know what is considered a normal range for compression, and then what is considered a high compression engine?

I will have to find the correct curve for this bike. I know the kit is PVL Digital Ignition 80115. (anyone have an ignition curve for this kit?)

Tomas, cylinder was checked for roundness by Eric Gorr in the US with the Woosner piston and then by a tuner in Perth (Ray Easson) with the ProX piston.  I am hearing you and maybe something was missed. When I get the new piston, there should be plenty of clearance but I will check again.
As for the oil, I may change brands and ratios.  I will speak to the tuner about it.
I am also thinking about taking it all back to stock to start with, and then adding the parts slowly and checking everything again as I go.

Thanks for your input and patience guys. Some of this is new to me, and just have to slowly work through it.

Cheers,



Title: Re: YZ125K Rebuild
Post by: ralph311 on October 22, 2017, 12:22:05 PM
Full marks for perseverance, I'd have gone completely postal by now. I got a bit lost in the thread but a couple of thoughts that might be of some use.....

If detonation is killing the motor seems to me that its at least possible for the problem to be caused by/resolvable by ignition timing alone, especially if you're confident it isn't running lean and you haven't put a timing light on it yet. So sorting that as a priority sounds sensible.

Also seems to me that a good place to start is to know what your ignition has been doing when the bike keeps seizing. If it were me... when I put it back together I'd set it up exactly how it was when it died and use a timing light and the torqsoft calculator to convert to degrees. Until you put a timing light on it you just don't know what its doing, you're guessing!

Then you can compare to the stock Yamaha advance. At least you will have a starting point that you can discuss with your tuner, which is another must do in my mind. He may be able to recommend something more appropriate for the compression/fuel you are running.

Also... afaik the best lubrication is castor oil. And whatever the initial cause, in the end you could say your problem is a lubrication failure. (I don't understand the fetish that some seem to have, putting the least lubrication into a two stroke that they think they can get away with) After all you've been thru.... geeze again if it were me I'd run that maxima 927 at 20-1, cross my fingers, kill a chicken and anything else I could think of to help keep it alive.  ;)

ps if you've been borrowing your buddy's super bargain special-for-you ebay dial gauge, it is metric and not imperial?? ;D
Title: Re: YZ125K Rebuild
Post by: GMC on October 22, 2017, 03:22:18 PM
My 2c worth;

Oil Brand
Seems you are running TTS, you will get many recommendations about oil brands but I doubt there is anything fundamentally wrong with TTS otherwise bikes would be dropping like flies all over the place.
I have swapped oil brands a few times over the years and I currently run TTS without drama and I also used it in the eighties without drama as well.
I doubt that the oil brand is the problem

Oil ratio
You will also get many recommendations about what oil ratio to use but if you’re running anything between 20 and 40 to one then you should be fine.
People run ratios inside this window all the time without drama. Changing the ratio will cause more jetting issues due to changing the viscosity of the fuel so if you’re running inside this ratio I would also leave well enough alone.
There may be decent argument for decreasing wear with more oil but I doubt it would straight up cause a seizure otherwise bikes would be dropping like flies all over the place.
I assume you run your other bikes on the same oil and ratio without problems!

Fuel flow
This one is often overlooked, if the gauze filter in the fuel tap is blocked or if you’re running a fuel filter you may be restricting fuel flow which will throw your jetting specs out the window.
You should take the fuel hose from the carby and hold it in the same shape as if it was on the carby and turn the tap on to see if you have decent fuel flow.

Piston marks
Pistons are made oval and tapered, the theory is due to more material around the crown and gudgeon is that they will expand to become round when at operating temperature, this same theory says that if they become hotter than intended then they will expand more to become out of round thus crating seize marks at certain points on the piston.
I doubt that Eric Gorr stuffed up the machining however some brands have misjudged the expansion rates for their pistons and rubbing the high spots is an old school trick to get them to spec.
Most modern pistons I thought were pretty much on the mark though.

Exhaust
People use all manner of brands without drama and I can’t see this as causing any problems unless the stinger/muffler core is the wrong size. A 125 should be approx. 23mm ID plus/minus 1mm
I have seen guys fit 125 mufflers on a 250 and wonder why it doesn’t run properly.
Even had a guy fit a 4T muffler to his 2T and wonder why it didn’t rev properly!

Carby size
Increasing the carby size will mean more air enters the motor at full throttle so you will need a bigger main jet than normal to compensate to the correct fuel/air ratio. What main jet people are running on smaller carbies will be irrelevant
You may have miscalculated this one!

Timing
Being an aftermarket ignition it will be a bit more complicated to set compared to stock.
It may even have an odd advance curve so checking this out thoroughly would be my first thing to check.

Multiple issues
Often problems can be caused by more than one issue, jetting alone may not cause it to seize and timing alone may not cause it to seize but both being a little bit out may push your specs over the edge.

Good luck, when you feel it’s doing your head in then sometimes it can be best to sleep on it

PS. Yes beware the European dial gauge!

Title: Re: YZ125K Rebuild
Post by: pecrazy on October 22, 2017, 05:11:36 PM
I'm no expert by any means but I always believed that a 4 corner seizure like that was caused by incorrect clearance, regardless of oil, oil ratio or timing.
Title: Re: YZ125K Rebuild
Post by: topari on October 22, 2017, 06:28:13 PM
I'm no expert by any means but I always believed that a 4 corner seizure like that was caused by incorrect clearance, regardless of oil, oil ratio or timing.

Agree, had a similar problem on a xr400. Installed a hi-comp piston in place of the standard. Full 4 corner seizure. The hi-comp piston had different clearances specification. Noob problem.
Title: Re: YZ125K Rebuild
Post by: evo550 on October 22, 2017, 08:02:53 PM
I'm no expert by any means but I always believed that a 4 corner seizure like that was caused by incorrect clearance, regardless of oil, oil ratio or timing.

Me too ...
Title: Re: YZ125K Rebuild
Post by: alexbrown64 on October 22, 2017, 09:11:18 PM
Thanks for the responses fellas. I will look at the muffler Geoff as its DG aftermarket. I set the bigger carb up exactly as the Yamaha race report recommended, but also went up on main and jetted needle richer.
4 corner seizure is clearance issue. My cast piston also had detonation. Famous tuner named Harry Klemm saw my pics and told me i need race fuel due to me having a high compression engine. I am not going to use race fuel, so it's check squish, lower compression, check and retard ignition, etc.
I think the high compression, low octane fuel caused detonation that has heated both the cast and forged piston beyond tolerances and grabbed on the 4 corners.
So, will check piston tolerances again, compression, air leaks, jetting, timing, muffler squish etc..

I also believe tts is ok. It was used by everyone in 83 at 25:1 and no issues. I run my other 125K and other bikes on the same Jerry of premix.

Fuel tap is new and flows freely.
Dial gauge is good quality.

I am working away, but when I get home, I will install new piston, check timing, swish, compression, muffler, leak down, then give engine to tuner to inspect and measure. See what he reckons.

One other thing, another member has had issues with his 125k, which has a worked engine. His was delivered with 2 base gaskets and had previously ran race gas before this. It may of been a way to reduce compression for normal fuel.

Cheers,


Title: Re: YZ125K Rebuild
Post by: OverTheHill on October 23, 2017, 08:46:48 AM
Looking back to find the seized piston. Just looks like not enough clearance initialy. Being yamaha & if a yam piston they probably only run about 2 thou at a point at the top of the curve of the cut away inlet. Maybe the ring got pinched on the exhaust side to start it all downhill slide to be seized on 4 corners. Not something like a water pump problem?, had an early water cooled KX80 where the impeller came unstuck & not turning 'at all'. In saying that son kept racing it hard for the day & never caused a problem luckily just thermosyphoning i suppose.
Title: Re: YZ125K Rebuild
Post by: Lozza on October 24, 2017, 11:33:01 AM

I found out my stroke is 50mm
My rod is 98mm centre to centre

When I use the torque soft app at 20* I get a value of 1.88mm

I have the Digital PVL, not an analogue one, and an internal rotor.  Not sure about windings etc.. I dont know my pvl cdi number yet, as I am working away. So, not sure what PVL ignition curve I have.  Would the curve not be closest to the curve on the bottom right?

My Yamaha curve in my manual shows about 26* btdc  at 4000 rpm

When I find out the correct value from pvl and then plug it into torqsoft, I assume I set the piston with my dial gauge at the given mm btdc, then make a mark on my outer stator and inner rotor that can be anywhere, but they must align.  Then start the bike and using the rpm gauge and timing light, bring the rpm to the correct range and check to see if the marks line up, and then adjust the stator a whisker to align the marks.  Does that process now sound correct?

Would this just test whether the ignition was working properly and set it to the recommended PVL baseline?  As even PVL states that the measurements they give are only a starting point.  I may need to go a lot more retarded for a higher compression engine no?
Also have to look at a leakdown test, a compression test, compression ratio test (Yamaha state 7.8-9.9:1) and squish band test. Yamaha recommends the squish for this bike at .8mm.  Does anyone know what is considered a normal range for compression, and then what is considered a high compression engine?

I will have to find the correct curve for this bike. I know the kit is PVL Digital Ignition 80115. (anyone have an ignition curve for this kit?)


Your process is close but you need to look at the curve closely as after the engine is running it will follow the pre-programmed curve inside the cdi not what you static set the stator/rotor to. 

PVL only have 4 curves to choose from. 1.2mm BTDC= 16* (I think your rod length is 100mm too) so when you set that to 16* every point on that curve will be +/- 16*. At the point where the curve says "0*" will you have what you first set the stator/rotor to. The digital curve at 4000 rpm is +22* so you will have 38* and at 11,000 you will be back to 16*. As you can see 38* is a wee bit more than 26* of the yamaha curve.

Have you measured the head volume? A water cooled engine will easy run 15-16:1 with 98 pump fuel. A high comp engine I would regard as +17:1. The Yamaha figure is the useless corrected compression ratio that uses the volume form top of exhaust port not full swept volume.
Squish is about right.
Title: Re: YZ125K Rebuild
Post by: alexbrown64 on October 25, 2017, 12:12:49 AM

I found out my stroke is 50mm
My rod is 98mm centre to centre

When I use the torque soft app at 20* I get a value of 1.88mm

I have the Digital PVL, not an analogue one, and an internal rotor.  Not sure about windings etc.. I dont know my pvl cdi number yet, as I am working away. So, not sure what PVL ignition curve I have.  Would the curve not be closest to the curve on the bottom right?

My Yamaha curve in my manual shows about 26* btdc  at 4000 rpm

When I find out the correct value from pvl and then plug it into torqsoft, I assume I set the piston with my dial gauge at the given mm btdc, then make a mark on my outer stator and inner rotor that can be anywhere, but they must align.  Then start the bike and using the rpm gauge and timing light, bring the rpm to the correct range and check to see if the marks line up, and then adjust the stator a whisker to align the marks.  Does that process now sound correct?

Would this just test whether the ignition was working properly and set it to the recommended PVL baseline?  As even PVL states that the measurements they give are only a starting point.  I may need to go a lot more retarded for a higher compression engine no?
Also have to look at a leakdown test, a compression test, compression ratio test (Yamaha state 7.8-9.9:1) and squish band test. Yamaha recommends the squish for this bike at .8mm.  Does anyone know what is considered a normal range for compression, and then what is considered a high compression engine?

I will have to find the correct curve for this bike. I know the kit is PVL Digital Ignition 80115. (anyone have an ignition curve for this kit?)


PVL only have 4 curves to choose from. 1.2mm BTDC= 16* (I think your rod length is 100mm too) so when you set that to 16* every point on that curve will be +/- 16*. At the point where the curve says "0*" will you have what you first set the stator/rotor to. The digital curve at 4000 rpm is +22* so you will have 38* and at 11,000 you will be back to 16*. As you can see 38* is a wee bit more than 26* of the yamaha curve.

Took me a while to get my head around what you are saying, but I believe you mean the digital curve in the PVL diagram is relative to "0". So when PVL say 22* at 4000 rpm, that would be as if you had your bike set at top dead centre.  When you reset your piston away from ("0" , TDC), you are affectively adding degrees to PVL's curve.  So, by using Torqsoft to calculate my crankangle at 1.2mm btdc, which gives me 16*, I have to add that to all the readings on the chart.  The 16* I set the bike at plus the 22* from the chart at 4000 rpm, which is the 38*.
When I use Torqsoft to calculate the angle at .8mm btdc I get 13*, which would take the affective advance at 4000 rpm to 35*.

So, the Yamaha curve (I will have to put a pic up at some stage), shows the degree readings with the bike already set at the Yamaha recommended 1.88* btdc for their standard system, which is indeed about 26* at 4000 rpm.

At wide open throttle though (11000 rpm) Yamaha's chart shows 13*.  PVL chart shows that the timing in the cdi has been retarded again back to "0", but add the 16* because of our 1.2mm movement of the piston and we have 16* again. 

Yep, got all that now, but they are relatively the same at wide open.  Dont ride the bike much at 4000 and it ran for 45 mins at these lower throttle openings when I was running it in. So, the PVL is not far off. And if i retard the timing to .8 mm btdc, i will be running 13* at 11000 and that would be the same as Yamaha.  In fact, i re-read the PVL documentation and it does state i should be running between 1 and 1.2 mm and even lower if i have a modified engine.

I will be taking the cylinder and head up to Ray Easson and he is going to measure the head volume. He also wants one of my standard heads to measure and compare.

Overthehill, at idle i checked the new rad fluid by opening the cap and i could see it pumping around the bike. The cylinder is fine, it only had aluminium smeared on it, no marks at all from a ring snagging.

On another less complicated note (my head hurts).. i have ordered a new Mikuni 34 mm carb, and have compared and ordered the necessary jets to run the bike as per Yamaha 1983. I will also adjust the needle and run a bigger main anyway to run the bike richer.
Also ordered the new ProX piston.

Used Oemcycle.com this time.  Anyone else starting to use them.  I got a bunch of parts really cheap and they gave me 3 postal options.. One of the options was free post!!  I have ordered nick nacks through their Ebay site, but their regular website is pretty good too.

Cheers,





Title: Re: YZ125K Rebuild
Post by: OverTheHill on October 25, 2017, 07:59:11 AM
Not sure what i said now but probably meant the ring getting pinched in the groove from overheating on exhaust side rather than snagged in the port but no worries. Just get the clearance checked with a new piston & if it's not a recent rebore then get it checked for wear around the exhaust port. Ran mine on methanol back in the day, was damn fast too. Had my 125G on meths too. Purple shell racing special it was called. Double the petrol price & used twice as much--but was fun times. Nothing wrong with my long term lol--what was the question again!!.
Title: Re: YZ125K Rebuild
Post by: Lozza on October 25, 2017, 11:22:47 AM
Over 30* is too much advance, then there is the little problem of the curve going from -10 to -19* (for ease of starting) between about 0-1000 rpm which means you would need static advance to be more than +20*. Where did you get the PVL from?
Using 1-1.2mm BTDC as a base would be OK with the non digital ignitions but I don't see any real advantage of any PVL curve over the standard curve.
Title: Re: YZ125K Rebuild
Post by: alexbrown64 on October 25, 2017, 03:57:21 PM
The pvl digital kit comes from penton racing in USA. 80115. I am using the digital chart you posted up Loz. Not sure if it's the curve in my Cdi. Pvl advertises these for the yz125. Do you think the ignition could be the problem?

I am putting a standard ignition on anyway for a while, but I am not sure about these mapping issues.
Title: Re: YZ125K Rebuild
Post by: justanothercgrader on October 25, 2017, 07:34:27 PM
Although you probably didn't buy it from him and he is no longer a dealer, i would try to contact Newmann on Vital mx for advice on setting up the PVL, try the "old school " section.

He should be able to clarify the set up.
Title: Re: YZ125K Rebuild
Post by: ralph311 on October 25, 2017, 08:19:47 PM
Still guessing re the PVL if you don't put a timing light on it.  :)
Title: Re: YZ125K Rebuild
Post by: Lozza on October 26, 2017, 11:28:26 AM
The pvl digital kit comes from penton racing in USA. 80115. I am using the digital chart you posted up Loz. Not sure if it's the curve in my Cdi. Pvl advertises these for the yz125. Do you think the ignition could be the problem?

I am putting a standard ignition on anyway for a while, but I am not sure about these mapping issues.
I don't think the ignition itself is the problem. Curve maybe , the piston crown will tell
Title: Re: YZ125K Rebuild
Post by: alexbrown64 on October 26, 2017, 03:16:39 PM
I have the Yamaha map which shows peak curve at 28* for piston set at 1.88 btdc.
I have hpi map which shows peak curve at 30* for piston set at 2mm btdc.
I have contacted pvl. They want to know all my part numbers. I wil have to get back to them in a few weeks.

I did get it through Newmann as he had an account with Penton.

Perhaps curve could be wrong. Lots to measure up and a puzzle to solve. I will run lots of tests, take lots of notes and give everything over to an expert for analysis.

Title: Re: YZ125K Rebuild
Post by: alexbrown64 on November 21, 2017, 06:57:54 PM
I stripped the bike down today and took pics of the PVL. I do have the digital cdi 537202.

(https://vufisq-bn1305.files.1drv.com/y4mSl-pZqrNMNZcmynVxqyMdGlssmPHqVNwHbb8WxexpeHwdOpn6ufHcwBH2xKc_vSFUiKjOyx9hy3MDW6H-xahaTYuQo1Pu4jEI-BeNgSwStWLv0bbL3PAUixYhwUvD9JlAQO6gqx3jxqItnAESLPEN0rzsg9hX-m19QNV3lmsYrWp5dshswXT-yXEiPb3_QD4MJWp1bBZJDv8EgDF8ot_kg?width=540&height=249&cropmode=none)

So, perhaps my ignition is advancing too much. I will have to re-read the last few pages of this thread to get my head all around it again, but it looks like at 4000rpm i am running 38* advance compared to the Yamaha 26*.
I also have the engine on the bench and am ready to assemble it with a lightly honed cylinder, new gaskets and new piston and ring.
I also have the plugs and gauges ready to do a leak down test and compression test.  I will also check my ignition advance settings using my dial gauge, as the motor is on the bench.

It will be going up to Ray Easson in the morning for further evaluation. I will be taking the other cylinder, a few more heads and the old piston.

I got my genuine Mikuni 34mm carb in the mail from oemcycles and will be fitting the jets that the YZ125K came with as standard. 6f21 needle etc..

Cheers,



Title: Re: YZ125K Rebuild
Post by: Lozza on November 21, 2017, 09:42:58 PM
with a dial gauge you are only checking a static amount of advance really needs to be set with a timing light
Title: Re: YZ125K Rebuild
Post by: alexbrown64 on November 22, 2017, 12:14:34 AM
Hey Loz, bike isnt running yet.. needs a lot of work to get it all up and running.  Engine is going up town to be checked over.  Just wanted to see if timing was still set at 1.2mm btdc and nothing drastic had changed. Tried to do it tonight and digital dial gauge had flat batteries.. its still going up in the morning..
I have emailed PVL in the US with my details, but whats the deal with having that timing curve in a digital cdi that is sold for 125's. I have printed out the curves, and will give to Ray Easson to look at.

Cheers,

Title: Re: YZ125K Rebuild
Post by: Lozza on November 22, 2017, 08:16:27 PM


(https://vufisq-bn1305.files.1drv.com/y4mSl-pZqrNMNZcmynVxqyMdGlssmPHqVNwHbb8WxexpeHwdOpn6ufHcwBH2xKc_vSFUiKjOyx9hy3MDW6H-xahaTYuQo1Pu4jEI-BeNgSwStWLv0bbL3PAUixYhwUvD9JlAQO6gqx3jxqItnAESLPEN0rzsg9hX-m19QNV3lmsYrWp5dshswXT-yXEiPb3_QD4MJWp1bBZJDv8EgDF8ot_kg?width=540&height=249&cropmode=none)



I still don't think relying on setting the timing by "x.xmm BTDC" is any good at all with this ignition. The only way it will be set correctly will be with the engine running at 4000 rpm. Look at how much the timing changes in 1500 rpm and the amount of static advance you're giving the ignition is added to this curve.
Title: Re: YZ125K Rebuild
Post by: alexbrown64 on November 22, 2017, 09:52:41 PM
I got an email back from pvl saying my stator is a 3000 winches one. He reckons my cdi was designed and tested for a 5000 winches stator and he can't provide a curve. Does this make sense?

Title: Re: YZ125K Rebuild
Post by: Momus on November 23, 2017, 02:52:36 AM
I'm going through something similar having been given a PVL analogue ignition supposedly to run a 500cc 4 stroke single, that when correctly i'd, was an 1800 windings 2 stroke unit for a kart.
 
PVL's site says, at least in regard to the analog systems " the approval of an ignition coil/stator unit combination must be registered by PVL. We urgently discourage random combinations with a view to obtaining a different ignition curve, as we do not know if the electronic components are compatible..."


Title: Re: YZ125K Rebuild
Post by: Lozza on November 23, 2017, 10:26:40 AM
Marcus if the stator is a 1443,1419 or 1424 I would buy the stator rotor if you don't want it the ignitions I use will work with those stators
I got an email back from pvl saying my stator is a 3000 winches one. He reckons my cdi was designed and tested for a 5000 winches stator and he can't provide a curve. Does this make sense?



Sort of I think the 5000 winds has more retard in the curve 3000 has less retard
Title: Re: YZ125K Rebuild
Post by: Momus on November 23, 2017, 08:47:22 PM
I'll have a look tonight Lozza.

Stator: 1442    54/A/18
Coil:    105458
Rotor:  940 - with a 3/4" bore from the B50 crank.
Title: Re: YZ125K Rebuild
Post by: ralph311 on November 24, 2017, 10:40:44 AM
I am putting a standard ignition on anyway for a while, but I am not sure about these mapping issues.

Yeah I vote for this. ;D Once you get it running reliably you're in a position to evaluate step by step modifications. Its hard to make progress when it keeps failing.
Title: Re: YZ125K Rebuild
Post by: alexbrown64 on November 24, 2017, 02:18:26 PM
Yep Ralph.  I got another email from PVL saying the curve is a combination of stator windings and the CDI.  They can't give me the curve for my 3000 windings (they call them winches) stator, but they are sending me the curve for the cdi i have with the 5000 windings stator. As loss said, my 3000 stator probably advances the the curve.
I took the motor up to Ray Easson and he is going to take some time and measure everything up again and check compression, squish, bore, clearance etc.. I showed him the curves i had.. and he was interested. I will give him more info from PVL as i get it.
I would like to check the values from the PVL ignition and see what curve i have been running. I am betting up around 10,000 rpm i am way advanced. I think most 125's should be around 13*, but the curve i have is showing about 16* and it may be more if i factor in the stator, as i believe the pvl curve that i have been posting up is for the 5000 windings stator.
Anyway, when it is all said and done, i am pretty much over it all and just want a reliable bike. So, the option is to put my Yamaha standard ignition on to start back at first base.

I think its parked up over Christmas... so this project wont be going very far until the new year...

Cheers,

Title: Re: YZ125K Rebuild
Post by: sleepy on November 24, 2017, 05:08:52 PM
I've seen the last of the air cooled 125's[G] do the same thing to the piston when the stock ignition goes off. When checked the stator coil resistance is low and the timing retards by about 10 to 15 deg at the top end. It is really important to check the timing up around 10k to see what it is, forget 4k as the motor is never there whilst being ridden hard. I would have thought if it was to much advance you would see detination damage as well. I'd think 16deg at 10k would be safe. 
Title: Re: YZ125K Rebuild
Post by: alexbrown64 on November 24, 2017, 07:28:06 PM
Hey Sleepy, the piston did show signs of detonation. It was all melted around the tip and was black underneath.
Yep, my G back in the day had a stater that went bad... bike just run like shit though.

This is what PVL has sent me and says it cdi 537202 with the 5000 windings stator.  I can't make heads or tails of the diagram.  Would i add my 16* to this or is this based on some sort of base setting with the bikes static advance already set?  I think the guys i am talking too are German, because i cant seem to get any straight answers.  I ask them what parts are suitable for my bike, and they waffle on about "change the setup from the ignition".  Hmmmmm

(https://u0fdhg-bn1305.files.1drv.com/y4mDq43bXipeLgaUHoxuHJMnYua079EziMWPrfZw7Qw2_Tm02PLiFoauzCKJXMHw_1rzPH9iclucwT8IQJKmhuOAbfJwJHMfqLreXf8U-qtWvX9sPoNTQRjQboWcHKtouWRZ9MpobgQmABknHqid-wjcMMRKEar-9KqhOR5udMOGQRZtur3WhxKZ6YOSg8NGeIWwuFWRmhENuFs4PBA1NUINw?width=660&height=469&cropmode=none)

Ive put an add up on facebook asking for a K genuine igniton setup.  Half my parts are junk or missing. Anyone have a full K ignition? I need stator, rotor, cdi and coil/plug lead/cap.  I am fedup with trialing PVL's box of parts....and may just put them up for sale. I have coil 466-100, rotor 9918, stator 1013 110mm, cdi 537-202.
I was also thinking HPI, but at the moment i just want to go standard and make sure the bike doesn't go kamikaze on me again.

Cheers,

Title: Re: YZ125K Rebuild
Post by: sleepy on November 24, 2017, 10:18:59 PM
That a very ordinary looking curve for a 125. To much timing change.
Don't know what their reference is. If I was trying to sort it I have a bench rig that I can run up to around 12k and then work back to the PVL timing mark.
If you were running it at those timing figures[black curve] it's no wonder it failed. Looks like 37deg at 10k.
Did you say you have the stock Yamaha curve to compare it to.

Title: Re: YZ125K Rebuild
Post by: alexbrown64 on November 24, 2017, 11:11:06 PM
I do sleepy and here it is.
Genuine 1983 YZ125K ignition curve and info. The reference point is set at 1.88 btdc using 50mm stroke and 98mm rod length.

(https://ukfdhg-bn1305.files.1drv.com/y4mMUPq4LnVqhJHOfxKYJpLe3ayfDVyywsDvwxvN45vet2gdttLzK0IueuPEOLvMfhbVuuQgQfcJI6QvhXzTgLrOf71qUBGmThvb8HHZSGlDzJCJiJ2JV8zw-L5sdoB8KIHfr1i4vDnnA2x97CjQpi-O3kyTNaD3noU88cnt0X0wrC-CsA9O3MPe5d7uzFAkrep_oSwoxYkS8KARMkfcE1fhw?width=644&height=660&cropmode=none)

Some other updates.  I have my new genuine Mikuni 34 to replace the 36. I have just ordered all the jets to get the original 34mm size carb back to stock.  290 main, 65 pilot, 6f21 jet needle.  Got these from nichecycle who have nice low shipping charges and have some hard to get bits.

Also lined up a genuine stator and coil.  Will use my original Yamaha rotor and cdi. But had to order a cdi rubber holder and rotor woodruff key from partzilla.  Partzilla also has really cheap shipping.  Only $6 from US.

Cheers,

Title: Re: YZ125K Rebuild
Post by: sleepy on November 25, 2017, 10:49:50 AM
From that curve your timing marks would align at 9k with 20 deg timing and max advance of 28 deg at 3k and the 11 k timing of 13 deg. That all way different to  the PVL. Did the PVL guys tell you which curve is yours, red or black.
The black curve may even work for a 500 single pommy motor with 1000 rpm timing at 8* giving max advance at 38* 7000rpm. Even that would be wrong as max advance should be around 3.5 to 4 k.
Don't know what to suggest you do with the PVL other than bin it. Could suggest HPI but have had very poor dealings over faulty product although most people seem to like them. 

Be careful with the carb as some of the new bodies have different size air correction jets and idle passage sizes. Which means just fitting the stock size jets, needles and needle jet doesn't get your carb the same as OEM.
Title: Re: YZ125K Rebuild
Post by: Lozza on November 27, 2017, 09:34:49 PM
Your only reference points you need are 1000 rpm and 3000 rpm check them with a timing light and disregard the 1.88mm static setting. At 1000 the standard ignition is 13* (which you can check with a drill turning the engine over and plug grounded out)and at 3000 it is 28* move the stator to get as close as possible to those 2 known points. The ignition timing will be fine across the range  checked at those 2 points. Don't be  afraid to remove the woodruff key altogether if you can't those 2 points to match.All the Hitachi ignitions have a similar curve. IIRC when I used one it was set to  13* static that came back to about 7* at 12,500.
Thats how you need to set the PVL at 4000 rpm vs the amount of advance you want which is +6deg as the PVL advances 22* at 4000 so you will have a total of 28*.
Title: Re: YZ125K Rebuild
Post by: sleepy on November 29, 2017, 10:38:04 AM
Using the BTDC method for the stock ignition is the most accurate method but you still need to check that the retard at the top end is working as it should or you could have another failure. Simple check for that is aim a timing light at the marks and if they don't line up at 9k it is faulty.
With the PVL until you know exactly what the timing curve is with your 5000 wind stator any sort timing check below 8 or 9k is asking for trouble.

Interesting how you had the same failure with a cast piston as you did with the Wossner, guess that it wasn't the fault of the Wossner after all.
Title: Re: YZ125K Rebuild
Post by: alexbrown64 on November 29, 2017, 11:45:02 PM
Thanks for all the input guys. I'm working away for a while so I've had to put the bike aside. I did achieve a bit though. I reassembled the engine with another new piston kit, and took the lot up to get measured and checked over.
Also ordered a genuine stator and coil, and have a spare Yamaha cdi.
Will do leak down test, timing light check and use my new standard size carb with Yamaha spec jets. The newer Mikunis may be a whisker different, but I am sure I will be in the ball park.
I will do all these mods, together with the recommendations and mods that Ray Easson is doing in regard to squish and compression.
Hopefully I will have a runner in the new year..

Updates later...
Cheers,
Title: Re: YZ125K Rebuild
Post by: alexbrown64 on April 30, 2018, 04:43:30 PM
Just a quick update.  Will be putting her back together soon.. just had a million and one other projects on the go..
Anyway, according to Ray Easson she was detonating, and the reason he believes is because she was built for high octane race fuel by Eric Gorr. He measured everything up and has added an extra base gasket.  Still wants me to check ignition etc..

I have everything to take her back to stock.  Stock size carb and jets, stock ignition etc.  I will put her back together with all the stock parts and slowly go from there..

Cheers,

Title: Re: YZ125K Rebuild
Post by: alexbrown64 on May 20, 2018, 06:47:53 PM
The Curse Continues...

There was a ride day at Coastal Park today.
I quickly cobbled the Euro YZ back together with a new 2mm oversize 58mm head gasket and new base gasket and some other fresh parts and got her running last night.

So me and a mate hit the track this morning.  About 100 bikes there by the time the fun started..

(https://8io5sg.bn.files.1drv.com/y4m9UdObvXQJ32SHhiL2uWnTySt08XZ8R9OQxCoTufa9eqo0LTwUH7GwhMt8ig3WSgIzb559HXSWLmTcyykk-EoPhOEVEmvE14u3gqGvhQoDy7DkoCWVPEDcZpr7BD06IwMgRxj1_q1sWbqGbO5AUHYcjIa2_aXjbQYtnxIv79D5tAaD9Rqqi8B5BhejDGfLGjJiJtSJN1wONXSm5fr2nglsQ?width=660&height=495&cropmode=none)

Bike is running like a champ for the first half of the warm up lap, but i do notice it feels a bit weak in 4th at high revs..
Then after 1 lap i hear a pop and she comes to a stop....
I push her back to the pits and notice that the radiator hose has popped of and no fluid.  I have cooked her. I obviously forgot to really tighten one of the hose clips, as it was hanging off.

Damage has been done..

(https://8so5sg.bn.files.1drv.com/y4mMIkp7bMZ0VfdNY7m3hft_h8xoUmfmpdU7iN6AYvR6HVUPSFXf00xv4dU2QcKZWJhcj57N19vYaNFOna_-UdHL3481oJplAD8zsq8W6zQWwmCxg5VK-P7ROrj13mExd65VZAhZrkcwRC2iSy-3Ccwawt95-Z3k7Q92EZhPl2phLutOSOYf05jMQLdvfvgwJfIotjdByOkasZskw1LW4XUFw?width=660&height=495&cropmode=none)

I think the cylinder is OK, as there are no scratches, just light scoring..

(https://8co5sg.bn.files.1drv.com/y4m-NbNXSCW1Nc3WQv-yUhePJsCPTB5Tig9XS-0twTHKZof1bwXKstITvSy2nr5eDElrrTgWznd21MRBQUxCiD6XP91ewAfLMKWXm1kj-Y17LdM7O6mKNbvx_piJpySPu1S-pOGCLDpkmqpDORUZ8rHuAQ8dG6GIJt-T3qjN0-mzMuXHOuCwfLEGpNCysRa4-_pqHuCy4VKheSoWtD3M6zi2g?width=660&height=495&cropmode=none)

OK, so i know i am up for a new piston kit, gasket kit, hone etc.. But... is it a tear down motor job.  Will i need to tear it apart and rebuild the big end, replace main bearings etc..
Or is there a shortcut? There was some small aluminium pieces around the edges of the cylinder.

Cheers,

Title: Re: YZ125K Rebuild
Post by: Hoony on May 20, 2018, 07:36:25 PM
its a total tear down i reckon. its not worth the risk NOT replacing the big end and mains.
i think you know that anyway but are hoping for the impossible.

it they let loose they you are back in the same boat.

thats a very tidy K you have there.
Title: Re: YZ125K Rebuild
Post by: GMC on May 20, 2018, 08:27:38 PM
While I agree with Hoony I did have a KX 250 that melted a piston twice in 2 years (Curse you Sea Lake)
A flush out and new piston and it was fine for several years.

You been a bit quiet of late, are your projects ramping up again now?
Title: Re: YZ125K Rebuild
Post by: alexbrown64 on May 21, 2018, 08:06:34 AM
Thanks for the input guys.  I might not risk it, and just order some new parts and rebuild her properly.
Yep, work and other projects have been getting in the way. I am fifo, plus i am separated and have my kids the whole time i am home.. bit of a juggling act.
I have the yellow YZ engine ready to go back in, and a timing light to check out the ignition.

I also have the G 125 project going, so hope to strip down the engine soon. Then hit you up Geoff for the pipe...

Cheers,