OzVMX Forum
Marque Remarks => Yamaha => Topic started by: YZ250H on September 13, 2007, 09:44:36 am
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Hi dudes,
Finally got the 125H/J going. It actually goes really well - lifts the front wheel 8) - for about 5 minutes ::). Then it just dies >:(. Plug seems to be a nice colour, so I think I've got the fuel reasonably close. Installed a new needle and seat, cleaned carb, checked float levels etc. It is also very hard to start (need to tow). Starts better with no throttle (ie load) and once above a certain rev level goes like a rocket (relatively speaking).
So I'm suspecting electrical or overheating. There seems to be a whole lot of gurgling noises coming from the head area when the bike has stopped. Is this a normal thing ? I can't see a whole lot of circulation when I remove the radiator cap. I thought the impellor looked pretty good.
The only other thing I can think of is a dodgy coil or something. Hilly has advised me to check the stators and the coil and the kill switch. The kill switch I can do, but I need guidance on the coils/stators. I know we have been through this a hundred times, but I can't seem to find the thread that explains it.
One more time for the uneducated please :-[.
TIA
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How does it stop?
Rev it's head off then die..Start miss firing... or just plain stop dead in it's tracks?
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Just stops dead in a progressive sort of way. As if you hit the kill switch then let it off. Because it dies a bit more every time it eventually just stops. A bit like it's running out of fuel, but it isn't (99.99% sure). I know, I know - I will check the kill switch first :-[, but it seems odd that it will go for almost the same length of time every time before dying - that's why i was thinking overheating or coil. Also forgot to mention that when I first got it it started second kick after being left for many months. Has gotten progressively harder to start. Now it's harder to start than a second hand lawnmower >:(
Found how to test ignition coil and kill switch in the manual. Just need help with stator coil testing.
Cheers ;)
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250H Check the flow of the fuel. If it keeps dying after the same length of time it sounds like not enough fuel is getting to the carb.(the filter could be blocked). Is the plug wet after it dies? If it is electrical the plug should be wet because you have lost spark but the fuel would still be coming in. Is the gurgling sound in the barrel/head or is it more in the exhaust pipe? Do it run (time wise) longer if you are just idling around than compaired with full throttle?
Do a fuel flow check. Remove the fuel hose at the tank and check the tap and then replace it and check the filter and then check going into the carb. The flow should be good and constant.
Is it using/losing coolant?
The coil, remove the spark plug cap (check the lead for good wire) and hold the lead about 6mm-8mm away from the engine and crank it over to see if you have a big fat spark.
When the stator fails (high speed coil) the bike just doesnt want to rev and has no power.
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DJ,
OK - so stators are OK. It is happy to rev once you get it going and has plenty of power for a 125.
I did the spark test with the plug still in the cap and earthed against the head. The spark was not what I would call fat. Small and weak would be a better description.
I'll try the fuel tests you suggest. Fuel upside the filter is fine. Haven't tried downside of filter, but shall do so. should be OK filter only installed recently. I'll give it another ride and see if the plug is wet. Can't tell if it idles longer as I've never actually let it idle and the idle screw isn't long enough to reach the slide (it's the wrong one - still waiting for Mr Yamaha "on back order")
The gurgling sound is in the head/barrel - definitely water. It does lose some fluid, but very slowly. I keep an eye on it and top it up regularly. How hot is the colling water supposed to get. I knew I should have stuck with a G model ;D. I will bypass the steering head with hoses. This will resolve the problem of the leak. I will get around to your fix solution soon.
So down to 4 things now - ingition coil, kill switch, fuel shortage or overheating (maybe). 3 of these I can now resolve thanks to your help. I'm going to the farm tonight, so I'll have a look at it.
Cheers
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HI
i had a e model tz250 that did the same thing and it turned out to be the plugs.try a new spark plug as you could have fouled a plug you said the spark is not a good fat one.
cheers
jimg
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250,
Also check the breather on the fuel cap, this is often overlooked, if it is blocked as the tank empties it will cause a vacume and prevent fuel flowing, To test run it until it stops then pull the fuel line off see how much fuel is coming out of the line, then undo the fuel cap and see if the flow increases. Does the fuel tap have a reserve? if so have you had it apart and re-assembled wrong and the "On" position is now the "Reserve" position? On the plug side of things, get yourself two new ones, run one until it dies, then fit the new one straight away, and see if it fires. I once had a maico that would just chew through plugs with no visual signs of fouling, they would just stop firing, on average lasting about 9 or 10 laps of a race track.
Could not rectify it, just got used to it. 3 new plugs to every race meeting.........beats me why they are the "must have" item in VMX.
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just a little concerned that you dont seem to have any coolant flow , you should be able to see flow in the radiator at idle,does the bike start after it dies or only when it cools down,it could be a partial nip up due to overheating,the only thing is it will get worse and eventually sieze, if it starts almost straight away after dying it is possibly a fuel concern (blocked fuel tap) or maybe something simple like float level not adjusted correctly (change of needle and seat),it is possible that its going like a rocket because its a tad lean, then the next on the list is that the source coils are on there last legs and just cant handle the heat causing them to open cicuit, you may need to get the bike to that point of dying and check for spark straight away, use a screwdriver in the spark cap and find a good earth, kick the bastard and see if you have spark.also do yourself a favour and check your gearbox oil and make sure its not pumping coolant into the gearbox due to the seal leaking,the tell tale sign is it will be milky in colour, hope this helps in some way , let us know what you find.CHEERS ;D ;D PS CHECK YOUR COIL LEAD IS SECURE IN THE COIL CAN IT BE REMOVED EASILY
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Tried to test the ignition coil and the kill switch last night. I found out the reason why the electrician left the multimeter at my place when he was doing a job there. The f$%#&ing thing doesn't work properly ;D ;D Thought I'd scored a multimeter, but instead scored a piece of crap !! That's Karma for you !!
I'll buy one today and see how I go. Lots of different things to look at now. Thanks guys. I'll check all these things one at a time over the week-end and let you know how I go. Should just be a process of elimination.
Cheers
T.J.B.
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250H it will be good to hear what is/was wrong with the 125H. Its always interesting to try to figure out a problem and get it corrected. Hope ya find the problem and let us(guessworkers) know what it was.
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Hi Guys,
Tested the coil and kill switch with my new multimeter 8). Kill switch seems fine with infinite resistance (open circuit) without the button pressed and bugger all rsisitance when the button is pressed, so that seems OK. The ignition coil may be another story. Clymer says 0.6 to 1 Ohm +-10% for primary coil and 5.6 to 6.2 K ohm +-20% for secondary (spark plug side). My readings are primary - 1.4 Ohms and Secondary 6.27. Primary according to Clymer NFG. Clymer says chuck it and get a new one - what do you guys say ??
I imagine like cars someone make an aftermarket hot up coil for bikes (???). Otherwise there is one on Ebay. The good news is the secondary on the 250 Coil doesn't come up to scratch either >:(, so aftermarket would be good (maybe i can get discount for bulk buys ;D). Anybody know ??
I will continue to go through the other stuff on here as it may be a combination of things.
Cheers ;)
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YZ250H i would say your coil is fine !
0.4 Ohm Resistance extra is negligible. as a matter of interest did you Zero your multimeter before testing the primary ? this is done by holding the 2 multimeter leads together when on OHMS scale and using the adjustment Potentiometer (dial) till the meter reads zero, i would suspect that this is your0.4 ohm error. BTW, i am an Electrician !
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No I didn't zero it :-[. That's why I'm a civil engineer not an electrician (or a mechanic) ;D.
I'll give it a crack and get the coil out of the bin :D :D
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as for any other electrical problems i can only summise that if the bike is getting hot and coils in the flywheel are getting hot it could possibly breaking down (coils shorting between turns) when hot , this can be a problem with bad insulation (enamel on the wiring) due to age.
also look for any plug in bad connections or worn insulation possibly touching the frame (earth shorting).
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Cleaned the contact of the coil to the frame, cleaned the plug. It push started quite easily with the choke on and stopped very shortlly after. Then it kick started first kick 8). It ran for the customary 5 mins then died true to form :(. Checked fuel flow below filter - all good. Drained carb from large plug in the bottom. Plenty of fuel in there. Fuel stopped flowing when I turned the fuel tap off and then flowed freely when I turned it back on. To me this would indicate the needle and seat is opening(???). On each stoppage the plug has been dry when the motor has stopped, but has been quite hot, so maybe the fuel evaporated ???. I'll try and get a video of bike running then stopping to see if that helps you guys at all.
Anyone any the wiser???. At the moment things seem to be pointing to the fuel side of things wouldn't you think?. Hoony was right about the multimeter. Both readings in tolerance, so the coil is OK - thanks Hoony - saved me on that one. I think I will pull the carb off and clean it again, check float levels etc. I'll go over the wiring (which looks pretty dodgy) today as well.
As far as the gurgling sounds go - the transmission oil still looks good. I put some new hoses on and bled the air out of the top of the head and it seems to have settled down nicely. Still losing water from the steering head. Nathan's got some hoses on the way, so I'll short circuit the steering head when thoose hoses get here.
I'll keep you posted.
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This is a tough one 250H. I will talk to a few friends over here and discribe what you have said and ask there advice. Do you think the motor is getting excessively hot? and have you done the timing? What jetting is in the carb?
I have a question for my mechanic friend about your bike, but before I ask you about it, I will ask him about an idea/thought I have just in case it is a stupid thought, then I will only get laughed at by 1 person and not the whole wide world ;) ;D
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have you tried kicking the bastard after it dies with a new spark plug in the cap or screw driver to see if you still have spark? you need to eliminate a temperature affected magneto coils , and maybe try a different cdi unit if you have one,is the coil lead secure in the coil, you need to check spark as soon as she dies, this will ensure everything electrical is good, then you can move on ::) will the coil lead unscrew out of the coil?, if it is long enough cut it where the coil lead screws in so its nice and clean then screw it back into the coil, this was my problem with my 125h run for 5 mins and die due to resistance change at the ignition coil lead not being a good contact in the coil screw, hopefully your coil lead screws out and you can see what i mean ;D ;D, let me know cheers (check spark when the bastard dies)
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had a bike doing similar thing to yours and found that the two vent pipes on carby were connected together instead of open to the outside,if you only have one vent pipe it may be blocked?
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Talked to my mechanic friend and he is saying what Bonehead is saying. You need to check the spark the moment she dies.
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Could simular to electrical probblems that were common in VL C/dore 6 Cyl's, Diode or transitor in the dizzy would die car would start & run for about 5 mins then stop. 2 ways to check - check spark at time of stopping or through bucket of water over dizzy.
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I reckon you blokes are onto something here. I had a closer look at the plug after it stopped last time the core was dry, but the outer still had some liquid on it. I cleaned out the carb and blew it out with the compressor - clean as a whistle (toobs too thanks Gorby - that's how I got stuff in me eye ::))
I've been running 20:1 Valvoline 'cause I just put her back together - I'll change to 33 to 1 next batch. I don't imagine it would cause this, but you never know.
So.... after going from suspecting electrical back to fuel, I'm now suspecting electrical again.
DJ - I thought the motor might be getting too hot due to the gurgling and boiling, but since I fixed a couple of hoses and bled the air out of the head it seems to have settled.
The way I see it there are only a few elements to this bloody electrical thing. Stators, coil, lead(s) and spark plug. I will as Boney suggests get a new spark plug and try the spark straight after she stops.
Does anyone know if the spark plug lead screws out of the coil as I don't want to break it :o I noticed during my wiring inspection the coil lead does have a rub mark on it from the throttle cable. That may cause the change of resistance thing Boney (??) I assume you can replace the high tension lead ???
I took a photo of the plug for you sickoes that are into that sort of thing !!!(http://i202.photobucket.com/albums/aa49/tbarsby/plugreduced.jpg)
Is the colour OK considering I'm running 20:1 (for about another litre) it is actually a bit lighter grey tahn the photo shows, but hopefully you get the idea (I have none).
The saga continues (on the week-end)
Cheers
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it's not running a resistor plug cap,they(old ones) tend to build up resistance when running a while from cold to operating temp,do the resistance thing with your multimeter,(over 5kohms, binit!!),if it's not resistor ignore this ;D
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Hey Tony wear ya safety glasses. Have you tried the stator off your 250 ?. I have 2 dodgy stators that i have to get checked and maybe rewound. Both were on engines i rebuilt ,both started up but after initial run they would only start once or just fire once,i had very weak yellow spark .The high resistance coil was open cicuit so i now have the YZ100 one in the 80K and the 125K in the 100. both have not missed a beat since i changed just the coils over off the backing plate . You need to check the resistance in the lead from the stator coils to the cdi the spec is in yuor book There is 3 wires cant remeber the colours there is a common wire between the coils that also has a soldered join near the coils this can cause drama's too. The upside to all this your second bike is goin to be a piece of piss cause you will know them inside out . Just dont go switching brands or you have to start all over again. good luck Hilly.
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yes the coil lead should screw out of the coil , is it the original coil , what happens is the anchor screw for the coil lead either corrodes away or due to vibration looses contact with the coil lead sporadically, just unscrew the coil lead and take a look in the coil and you should see the anchor screw if this is not there then i would suggest a new coil , if all is ok cut a little bit off your coil lead you will see what i mean, let me know cheers bonehead. ( you still need to check spark when she dies) ::) ::)
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OK,
On Boney's and DJ's advice I pulled the plug after she died. It was almost dark by then and it was much easier to see the the spark (yes it was there). SOOO we are back to fuel again which has me really stuffed :-\ :-\.
Will start on the kick start with choke on and wide open throttle. Symptoms have changed slightly now she only runs for a minute as though it's got about a teaspoon full of fuel in it then dies. Runs longer at lower revs. Leave it a few minutes same thing - jump starts easily, runs for a minute then dies.
I think we are finally on a winner here dudes 8) 8). I'll pull the whole fuel system off clean it and start again - starting from the fuel cap (which seems to vent OK).
I was thinking the other day that maybe Mr Yamaha sold me the wrong needle and seat ???. You wouldn't think so.
Hilly, I was going to take the video, but 1 minute of riding would be nothing more than embarrassing :-[ :-[ :-[
This weekend - fuel system again. New fuel hoses, new filter, flush the tank, clean the vent holes in the cap. Clean the carb (again), set the float levels (again - maybe I'm doing this wrong). Change fuel mixture to 33:1.
Any other suggestions ?? You blokes sick of talking about this yet ?? Mind you for a newbie would be a great trouble shooting guide as you blokes have almost exhausted the list of things that can go wrong and given of much of your experiences - THANKS :).
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250H what pilot jet are you running? There isnt an obstruction in the exhaust pipe ;)?
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good thought DJ.
is the airbox and airbox manofold also clear to breathe ?
many years ago a work mate had a XL185 and it would only run for 5 mins before stopping then when the plug was pulled out it was sooty.
ended up being he had spare spark plugs stored in the air breather holes along with some rags,
no air = no go!
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hey what pilot jet are you running , was the plug wet when you pulled it out, how good was the spark, it is possible that the pilot jet is too large and your running to rich on the pilot and killing it with fuel, had a 250 h do that and also sucking in oil from the gearbox due to crankseals not sealing, fouling the spark plug, these are just another combination of things to look for , does it blow a lot of smoke when it fires back up after bump starting it, i dont believe you have a fuel flow problem unless you are blind and cant see the obstruction :P ;D maybe also your oil to fuel ratio is incorrect , are you measuring it correctly this can cause fouling of the plug, you still havent answered my question as whether you have checked your coil lead as i have explained , just holding it at a different angle could still give you a spark , was it a fat blue spark, does the lead screw out of the coil,you really need to check this for good continuity to totally eliminate this concern, if it was a fuel concern like a blockage you would have spied it by know, if it was a blocked exhauast it possiblly would not even start or rev, if pain persists see a doctor (i may need to see this bike)CHEERS BONEHEAD :-\ :-\
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Geez you blokes ask a lot of hard questions ;D!!
I don't know what pilot jet I am running - how do I tell ?
Airbox and airbox manifold is clear - filter element is new unipart oiled not too much
The spark was good and fat (the sun had gone down) and blue, all other times have been in the daylight when maybe I couldn't see it as well. The core of the plug was dry, but there was an oily residue on the outside part. It will jump start now quite easily with the choke out (without cleaning the plug in between).
It does blow a tiny bit of darker smoke, then white smoke when it first starts up then clears very quickly. I'm with you boney, I'm pretty sure I don't have a fuel obstruction, but the way I'm going I'm not too sure of anything any more :-\. I did just get my first set of reading glasses (old age is setting in), so going blind could be a possibility ;D ;D
Oil to fuel is 20:1 (fuel to oil), but I will change that now that it has run for a bit with the richer mixture after being put back together.
I didn't try the coil lead :-[ :-[ but will this weekend. I tried the one of the 250 and I'm pretty sure it doesn't screw out. I didn't want to get too ham fisted with it for fear of buggering it. The cap that goes on the plug on the 125 does screw out, but seems to have a pretty good connection with the copper inner on the lead. Exhaust seems to flow out pretty well and makes a hell of a racket, but there is an oily residue sort of dripping out. It did rev out very well, but doesn't now. My patience is running out fast, so i might buy a new coil just to rule that out - where would I get one ? If I can't get this bloody thing sorted soon my startegy will be to start replacing bits with new ones (at the cost of my other restos :'().
My other thought was burn it and buy a Honda :D
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Heres a coil...
http://cgi.ebay.com/ebaymotors/Yamaha-YZ-125-Ignition-Coil-74-89-OEM-Replacement-NEW_W0QQcmdZViewItemQQcategoryZ35594QQihZ012QQitemZ220151685893QQrdZ1QQsspagenameZWDVW
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Thanks CG - I'm onto it. Even if it turns out not to be the coil it doesn't hurt to have a spare hanging around.
You are the ebay master - Cheers ;)
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white smoke =Not good.
you my son have a water leak plain and simple.
fix that with a new gasket and a lapped head and barrel and I kind of think all your woes will be gone ;)
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I will investigate Pokey - thanks. I struggle to find what else it might be, so you just could have it.
I'd still like to find out how to work out the pilot jet size. Will order some new gaskets. What is involved in lapping the head and barrel (and don't say running around it 3 times ;D ;D - I could see that coming from someone on here)
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Bugger stole my line ;D
seeing as the steering head has water issues with corrossion and what not it stands to reason the other journals would do aswell. the tell tale is that white smoke. water plus exhaust gases make white smoke that can only come from the combustion chamber so as the queen of hearts said"Off with its head"
Lapping isnt hard just labourious.
grab a a nice sheet of float glass( an oldhouse window will do) as its a smooth flat surface, an also a sheet or several of fine grade wet and dry paper (start with 1200 then go to 1500 or higher) and some oil.
Now make slow figure 8's with the head. add oil to the job to flush the build up of crap away . in about an hour you should have a nice flat smooth surface ..Take your time .
Next do the barrel but you will need to remove the studs. wash with warm soapy water after the job is done to remove any crap in the barrel or transfers
if you dont feel like doing that put it into a machine shop for the work.
Its not hard just time consuming.
do check the surfaces with bluing ink to make sure they are flat. I use a texta with the same results cept it dont look as flash as the blue.
To check the main jet just whip the bowl off the carb and have a look at it, is a number stamped into the jet.
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I'd still like to find out how to work out the pilot jet size. Will order some new gaskets.
the pilot is the little jet not the big one, undo the float bowl and you will see a little brass end with a flat blade head on it, it willbe reccessed so you need the right sized screw driver to fit down in the hole to reach it. It will undo anticlockwise, the # number will be stamped on the side if its genuine it will be like a little tube with a hole i the top, a thread then a few holes in its side. youll figure it out. while you have the carby in your hand remove the main jet, slider , needle - and write down every number from them in your race diary.
If you dont have a note book for each bike start one, every time you do somthing on that bike write it in, you change the rings, turn a screw in our out, every time you ride it write it down, how it handled, what the wether was like every thing, even how long it took you to get to the track. If you do that you will never be late, you will never be unprepared, and you will never not no what set up you should have or currently have on the bike TODAY. ;)
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250H the standard pilot jet is #80 and the air screw should be 1.5 turns out and the needle is a 6F21 clip position middle(3). The main jet is a 340 and the needle jet is a P8.
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Consider both of those jobs done boys. I will report back after the week-end on the jet numbers. The lapping may take a bit longer by the sound of it, but I'll give it a go.
Pokey I assume you put the wet and dry on the sheet of glass between the head and the glass ::). To check the flatness (pretty sure that's not actually a word) do you put the nikko pen on the head and then rub it on the sheet of paper. Any low bits still have nikko on them. Is that the idea ??
Freaky, the note book idea is excellent - especially when your memory is like mine (again, old age taking over ;D)
Thanks for spending the time on a newbie wannabe. I'm sure there will be heaps of other people getting a lot out of this too.
Cheers ;)
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Thats affirmative on all counts YZ250H, "IF" either of the surfaces show pitting get them machined or you will be thier lapping for a week. Take your time and slow figure 8's
good onya for givin it a go.
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250H if it is a leaky head gasket (o-ring) the piston will probably look very clean like it has been waterblasted, there probably wont be any carbon build up on the top of it and will look shiney.
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You should be able to check for a top end leak with a compression tester . If it's leaking water into the cylinder it could be corroded through the cylinder ,but if it was your crankcase would fill up with coolant when not running .
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Lapping isnt hard just labourious.
grab a a nice sheet of float glass( an oldhouse window will do) as its a smooth flat surface, an also a sheet or several of fine grade wet and dry paper (start with 1200 then go to 1500 or higher) and some oil.
Now make slow figure 8's with the head. add oil to the job to flush the build up of crap away . in about an hour you should have a nice flat smooth surface ..Take your time .
Next do the barrel but you will need to remove the studs. wash with warm soapy water after the job is done to remove any crap in the barrel or transfers
Pokey that's good info, you should add this to resto Tips
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As far as I can tell it all looked pretty good when I put it back together - piston and rings were new. My father inlaw who used to be a diesel fitter suggested I grease the o rings before installing them. I thought that was a bit odd at the time, but who am I to argue with the old codger. The surfaces of the bore, head and cylinder looked to be Ok, but you can't tell by looks obviously. Soooo - I'm making the hit prediction that it may be as DJ suggests. New orings are ordered and I'll do the flatness test to make sure. The do probably the only lapping I'll ever do in my life :D :D
Hoony, IMHO all the stuff on here is gold.
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geeze #80 sounds a big pilot, these things cant run the old Mukuni vm's then, they on a kehin or some kinda pumpa ? what i would have thought would be under #45 , but then i know nothing about anything from 75 - 85
i Was MIA that whole time.
One minute i had a 125 elsinore ---> the next time, i sat on somthing i had a xr250f and a Rz250R.
did'nt realise they made bikes in those years :-[ eeeeek
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jesus a #80 pilot jet my mates yz 250 h had that as a pilot and it would run and die, i believe thats far too big for your 125 , is the carby for your modle or did you source it somewhere else?, i dont believe its coolant entering the cylinder as you are not experiencing a missfire, if it is blowing white smoke on restarting the bastard >:( you may have a leaking crank seal or a seal in back to front and is sucking oil in from the gear box,you may even have a worn area where the seal runs on the crankshaft allowing oil to enter the cylinder and causing the spark to go out . how long has it been since the rebuild ,have you put to much oil down the bore when assembling , this can cause also the same effect as a leaking crank seal, if you are sure the spark is good then i believe you , if you run the bike on a stand will it die or only when the bike is under load, we are getting closer to resolving this concern , white smoke strange smell could be a clue. cheers BONEHEAD
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The way 250H explains the way he has to start the bike,(choke on and full throttle) tells me that his pilot jet is to small(maybe a 60) which is what a YZ125G runs as standard. I have always found that the standard yammie settings are pretty close. If the carb on the bike has 4V2-00 on it then it is the correct carb. If he is running boysen reeds the standard setting maybe to rich but it doesnt sound like that to me. Yeah Bonehead a YZ250H does run a 80 pilot but the slide cut-away is 3 and the needle jet is a Q-0 and needle 6F16. All this is in a 38mm carb not a 34mm as the 125H. The float level for the YZ125H should be 23.4mm
I can understand suzuki boys thinking that an 80 pilot jet is huge because they seem to run 30-45 pilots but, they also run different needles etc.
But anyway, if there is another problem (leaky head gasket or something else) the pilot jet wont be to much of a concern untill the main problem is resolved.
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Hi guys,
Carb is definitely 4V2-00 - that's one thing I'm sure of. I haven't had the reed block out, but will when I pull the cylinder off. I'll also check in the crank case to make sure there isn't any moisture in there. Also look for pinholes or pitting in cylinder/head. I assume Boysen reeds have some sort of identifying mark???.
I don't think I put too much oil in the cylinder when I put it back together - that's 'cause I didn't put any at all ::).
I had a thought that the stuff weeping from the exhaust may be moisture (from the combustion chamber via head gaskets) mixed with the carbon that was already in the exhaust ???
Does the pilot jet control low or high speed operation ?? It runs loud and strong once it gets on the pipe (sounds very much like Hilly's 100) 8).
Boney has opened a whole new can of worms with the crank seals. From what I could tell they seemed to be new as they still had all the texturing on them and where sealed with the same sealant as the cases. I assume this had not been done that long ago - maybe when they put in the new piston and rings ???. The seal on the ignition side was a tiny bit crooked - only a poofteenth. I will keep trying the spark when she dies to satisfy myself (and you guys) that it isn't a spark problem.
I checked the float level last time, but will do it again when I've got the carby off. Is there a particular point to measure it at. I have a Clymer manual and have been following that closely (when I can work out which bloody model they are talking about).
I'll try the carb jets etc, lap the head and cylinder, check the reeds are yamaha. Then it may be down to more serious business as Boney suggests. If I have to pull it down again I will get Mr Yamaha to put it back together this time just to be sure.
I'm with Boney on this one. I think we are getting closer. 8)
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wow wow wow , sealant on the crankseals, did you happen to check the gearbox side crankseal as this is the one that lets oil in the crank area when it is worn or put in the wrong way or if sealant is used to try and mask a concern temporarily, normally when just doing rings you dont have to strip down the cases unless you have had a major failure, so i take it that this engine was semi assembled or was slapped together by the previous owner ??? who bought some no more gaps and said this will do for 5 mins of fun,i think you need to inspect the crankseals i believe its sucking in gearbox oil and killing it. cheers BONEHEAD
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Yeah Bonehead (wow wow wow) I agree. It sounds like the crank seals aint the best if sealant has been used to hold them in place.
The pilot jet is for first eighth throttle. On the reeds just make sure they arent broken and that they are closed and not sticking up.
The crank seals can be replaced without splitting the cases. And when you replace the barrel, make the piston go fully down and check that it has opened up the transfer ports fully(if not you will need to put a thicker base gasket in) and then move the piston to the top of the barrel to check the hieght. Then back the piston down about 5mm and get to little pieces of solder(about 10mm long) and put them on top of the piston(from the cylinder wall inwards at opposite sides of the piston). Bolt the head on and slowly crank the piston over so the it goes through top dead centre. Dont crank it over fully or the little pieces of solder will fall in the crankcases. Remove the head and get the 2 pieces of solder and measure the flatten parts. This is an easy way of measuring the squash band. It should be greater than 1.1mm-1.2mm. This is good as it well help when timing the bike to get it to run properly. It also will aid in eliminating (pinking). anyway YZ250H good luck.
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c mon c mon did you get the chance to test the bike over the weekend, im still keen to see what the out come of this senario is, keep us informed i want hear the good news, good news that you have found the cause or good news that we have helped in locating the concern, ;) ;) cheers BONEHEAD.
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Sorry Boney,
No progress this week-end. Too busy working on the farm - don't you hate it when life gets in the way of fun. I did pull the carby off and bring it home, so after the weekend I'll know the jet sizes and float height. After that it's down to lapping the head. Head O rings haven't arrived yet anyway. I think I will try the water leak theory first. If that doesn't work I'll have to pull the motor out. I have a minor oil seep between the cases that is annoying me, so it looks like back to square one. I'll do the crank seals while I'm there - just to be sure.
That should solve 2 of the big theories. If that doesn't work I'm back to the little stuff again.
Don't worry - I haven't given up on it. ;)
One thing I neglected to tell all you blokes is it has a boost bottle fitted on a 5x5 manifold. That may change the jetting slightly (???).
I'm working on it ::).
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delete the thread, remove all traces of your name, then list it on ebay as a fresh barn find condition unkown and forget it and buy a good Pre 75 ;) anything with water is just 1 to many elemants. >:( See its all fung su.
its the cosmic triangle : metal (spark plug), air (via air filta ) and earth ( oil/ fuel) = 3 point balance, if you go adding water in there it just all gets umbalanced. :o
just face it YZ, your battliing the forces of nature here, no good can come of it;
be gone freaky bike back to your maker ! selling is the preferred over a tribal burying. ( although im sure if you took it to the DT nats they would throwit on the fire for you ) ;D
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FREAKY YOUR OUT THERE IN NOWHERE LAND ;D i beleive in the spirit of solving lifes mistries ,like why do we need motor cycles , why do we need 2 stokes , why do we need the niggly concerns, why do we need to believe we can fix them, why do we believe we have done our best , why do we believe in god why why why ? :o because im on holidays and had to many beers and im feeling emotional and i believe we can save this bike.IF IT DONT RUN SELL IT TO ME .
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No way dude. I won't be selling it !! I am determined to get this bugger going. Then I hope to race it. If nothing else I have learnt a lot about this motor. It will go - when it does I will post Hilly's video 8)
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I only hope that i can still turn the computer on when you do .Hhhmmm i'm getting old
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:D :D :D :D
It's a fair cop Hilly. It has taken me a rather long time. Close now though.
Maybe by the time I'm finished we will be able to turn the computer on by mind control ;D
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GUYS CHECK WHAT I FOUND ;D ;D,look at my post RED ALERT 125 H ;D ;D SOMEONE LEND ME MONEY ??? ???
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I'm onto it this week-end. Plan is to remove motor and send bottom end to Mr yamaha for resealing case halves with his secret sealant (stag didn't work) and installing new crank seals. I will lap the head (thanks Pokey) and put it back together when Mr Yamaha is finished. Then we try again ::).
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Stag ??? W.T.F I think that's for plumbers cracks mate . Anyway if you get the bottom end done properly you should be right and hopefully have running some time next year ??. C'mon Tony pull ya finger out and get this sucker running .
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Ok Ok, I'm on it - Geez you nag like my missus :P :P :P. She even asked me the other day when the bike was going to be running again - apparently the 250 resto should be going faster too :o :o. I've had 2 week-ends at home and the bike is at the farm - poor excuse I know :-[, but I have enjoyed being able to sit and have a beer (or two).
I should reveal wether the water has been leaking into the combustion chamber tomorrow. I will post photos if I find anything.
Got the new head gaskets (O Rings), sheet of glass, nikko pens, oil and wet and dry, so should all be ready to go back together next week-end. I will put pressure on myself now by saying I will post a video of bike going on Monday 29th (this year ;D). Then we can officially declare this thread dead and burried 8)
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Update for anyone that GAS :-\. I drained the oil and apparently while I wasn't looking someone replaced it with thickened cream. So after all that there is water in the oil. I swear it looked Ok when I checked it before. What does that mean ? I know it means a water leak, but from what I can see there are bugger all places it can get in. Perhaps the seal on the impeller ??. It is interesting that the barrel has a bit of a rusty film on it and you can see splash marks where the carbon from the top of the piston has splashed onto the bore.
I have checked the reed valves - all good there 8). I have lapped the heads thanks pokey. After the first round of 1200 I decided to go back to 400 as there was a bit of pitting especially on the barrel. I'll post some photos later if anyone is interested.
So at the moment motor is out and split ready for Mr Yamaha to seal the cases for me and replace the crank seals. Lapped head and new gaskets hopefully will be an end to my woes.
Anyone else got any suggestions as I put it back together (again)
Should I use some sort of sealant between the barrel and the head or just rely on the Orings to do all the work ?
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YZ250H,
you need to check all around the water pump housing for any pin holes to oil side of case. i am by no means a yamaha expert (that's Hilly, Nathan & the Bonester) but i do know Honda's and they all have a problem with electrolysis in this area, also check the water pump shaft for wear where the seal sits as the seals do wear the shaft (on honda's anyway). good luck mate, i have been following this thread with interest and want to know the final outcome.
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YZ250H
Dont use any sealant between the head and barrel, the O-rings do a good job. But replace the water pump seal (93103-12119).
Good luck
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A couple of things I have checked.
Reed block looks OK to me. They seem to close nice and tightly. Maybe you can identify it from the photo ???
(http://i202.photobucket.com/albums/aa49/tbarsby/reedblockreduced.jpg)
Pokey,
Is this good enough - note a couple of minor pits remain. How good do they need to be ?
(http://i202.photobucket.com/albums/aa49/tbarsby/headandbarrelreduced.jpg)
My major concern is the clutch basket at the moment. The other one was eaten out the same. The gears don't seem to be meshing properly and I can't see from the parts book that there is a washer added (or missing). Any ideas.
(http://i202.photobucket.com/albums/aa49/tbarsby/Clutchbasketreduced.jpg)
I've ordred the new water pump seal and priced a new impellor with shaft $65.60 :o :o Do you think it wise to just try the seal first ??
Cheers
T.J.B.
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Try the seal, unless you think you really need the new impellor shaft. The mating surfacers for the head and barrel look ok. Has the clutch basket come loose at some time? There are 2 washers on the clutch, one between the bearing and the basket and then one between the basket and the clutch boss. (90201-174E1). Make sure you have a lock-tab washer on so the main nut doesnt come loose.
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water pump impellar shaft may be ok , did you check if it is worn where the seal (seals) runs on it ?
question for DJ Racing do the yamaha's YZ125 H's run 2 seals or one ?
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The YZ125H/J run one waterpump seal (93103-12119) which is ID-12mm OD-31mm W-13.5mm.
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Bit hard for a picture to convey truness of surfaces. thats what engineering ink is for. Can also check with a straight edge and feeler gauges but the ink is best and easiest. It does look like you have done an okay job on them.
as long as you have a decent surface around all journals and no high points she should be right but do check with the ink.
I can i believe see one pit on the head that may be on the combustion/water sealing surface, rub it out if you can. If its pretty deep fill it with sealant like stag or a hi temp ceramic epoxy then a rub after it hardens and finishes shrinking.
looks like its coming along fine
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im back from holidays ;D ;D and looks like you have possibly found the concern with the bike, like i suggested before if the gearbox oil is milky you have a coolant leak from the waterpump seal and possibly a worn shaft on the impeller, this inturn creates pressure build up in the crankcase due to the extra fluid entering but should expell via the crankcase breather unless the crankseals are worn when then it will enter the combustion chamber causing it to not run, rust in the bore suggests this ,as when left sitting the electolisis process starts, DO NOT USE STAG, this is only used for putting in welsh plugs in V8 1970 - on vehicles , as far as the clutch basket goes , looks like it has run loose, anyway im keen to see this bitch run ,its good to be back on board, CHEERS ;D ;D
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Boney, I thought a sniper had got ya or something ;D
I have since learnt from Hilly that stag is only good for filling plumbers cracks (which we get around our house occasionally :D)
Knowing what I know now I'm pretty sure there was water leaking in everywhere (at the head and at the impellor seal). I haven't looked at the shaft, but will this week-end.
I will have another crack at the head lapping. I used the Nikko pen and it seemed to be flat as a tack, so should be OK. That pit you see on the head is on the outside of the sealing area of the inner O'ring, but I will do some more lapping and see if I can get it out. It took me a long time to get it to this and I basically got the sh1ts with it by the end. I was having a beer while I was doing it and there was quite a few empties hanging around by the time I finished :-[. For some reason the number 8 keeps coming into my head ;D
Hopefully new head O rings and flat surfaces, new crank seals, SEALED case halves and impellor seal will solve the bigger problems and then I can get onto the smaller stuff.
The clutch basket was done up with the impact wrench and has a locking tab. I will have another look at the washers as I may have overlooked something. I may have one of the washers in the wrong place. I'll make certain on reassembly. I put everything back together as I found it, so maybe the "mechanic" that put it back together before me got it wrong. Time will tell (not too much time Hilly ;D)
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Yeah lapping heads is a boring bastard of a job and the closer you get to having all the pits/dents removed the longer it seems to take ;) ;D
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I actually have to confess to starting the second piece (barrel) with coarser paper than 1500 :-[
Patience is a virtue I don't have a lot of.
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YOU NEED TO DRINK MORE BEER , as you work, you also may require to use your imagination, for example what could you do with the latest pin up girl from the magazine you just bought ;D or do the lawns need mowing ???or am i paying enough attention to my wife ::)or WILL THIS THING EVER RUN ;D cheers ;D oh the joys ,lets hope its all ok ;)
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Sorry Dudes,
Mr Yamaha did not come through with his promise of having the case halves ready by Friday >:( so it's next monday for the video.
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Dont worry YZ250H, it has been good trying to figure out the problem, but I'm sure by now you wish you had the bike up and running ;D ;)
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You're not wrong there DJ. Talk about trial by ordeal on my first VMXer :o ;D
I had a brain wave (rare for me) over the week-end that I think will definitely confirm it is water related. When I first got the bike it hadn't been started for a long, long time. I just mixed up some fuel, literally 3 kicks and away she went 8). I could only ride it around for a few minutes at a time 'cause the water pump cover was missing and no water in a watercooled bike I'm guessing is a no no. SOOOO I put a new cover on and filled her up with water. That's when the trouble started. It amazing what 20/20 hindsight can do. I'm still not counting my chickens yet, but I reckon we are most of the way there 8) I still have a long way to go before I have the knowledge of you blokes, but believe me I have learn't a hell of a lot about this bike and now feel quite comfortable delving into splitting cases etc. Thanks once again to all you guys for your tips and ideas. Should set me up well for the other restos I have to do. Next comes the 250 8) 8) (now that I have something going to ride) and Nathan's 125H 8) - then the others.
It seems like forever ago that this whole saga started with a wayward bolt jamming in the clutch gears.
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um you rode the bike with out any sought of cooling ? and a loose bolt caused the wear on the clutch drum? are you serious? was this whole post a HOAX >:( did you have this so called brain wave before or after you decided to create this ,i ask you would you drain the coolant from your car and drive it? NO NO NO >:(,so now tell me has the bike now had top end re build such as new piston and bore,,and i trust mister yamaha has assembled the bottom end correctly , i know this is a learnig curve but you must know the basics before even touching a spanner,GOODLUCK WITH THE 250 :P
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No no no - I'm not THAT stupid. I only ran it for about 2 minutes - not even long enough for the head to get slightly warm - I only did this twice - sorry, enthusiasm got the better of me :-[ :-[ it was the first day I got it home and I HAD to see if it went. The very next week-end on went the water pump cover (and coolant).
Of course the post insn't a hoax, why would I do that ???
The bolt in the clutch was nothing to do with this thread - it's a long long time ago - I think before you even came on here. There was a bolt that wasn't required that rattled loose and jammed in the gears (from the previous person) siezing the bike (others would remember).
(http://i202.photobucket.com/albums/aa49/tbarsby/seizure.jpg)
Bike came with new piston and rings installed.
I will take your comments re touching spanners on board.
There is no water anywhere to be seen on the 250 - thank god
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mmm, enthusiasm can be the enemy,it can cause kaos in every part of life, i may have been over enthusiastic myself on the odd ocassion,anyway any news on the bottom end im still keen to see this bike run ;D i wish to retract my entusiastic comments as i understand that this is a learning curve, i will still help with any concerns that arise on any of your projects. ;) ;D cheers BONEHEAD
ps got the seat back for the 250g looks fantastic.
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Took the clutch cover in to Mr Yamaha yesterday - he's going to replace the seal for me on the impellor, check the shaft for wear and replace the seal on the gear shift shaft.
He's resealing the cases with the good stuff (I'll find out what it is and tell everyone - no good keeping it a secret) and replacing the crank seals.
Right from the start I had reservations about the 125H being water cooled - now I've got 2 of the little buggers. Should have made them 125 G's instead ;D
Boney, I would and do appreciate your help with this stuff (as with others). You never know - one day I might have learnt enough from you blokes to help someone else :o :o. I know I have a long way to go :-[.
Photos of the seat installed please - where did the cover come from - I've heard mixed stories about different suppliers of them too. The pipe looks great - I was going to steer clear of them 'cause XYZ had a bad communication wrap, but if Les does the hard yards for you then I might reconsider.
I deserved a bollocking for running it without coolant as it was pretty dopey :-[. Lesson learnt. Enthusiasm is sometimes misplaced ::).
Cheers ;)
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The sealant they use is Yamabond 5, it is a grey looking sealant used for bonding engine cases together.
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sooooooo! did you get it running yet or is there still a concern :D
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I was wondering how long it would be 'till someone was on my case ::) ::). I thought everyone had got the sh1ts with this thread and forgotten about it. Lord knows it has been going long enough. I think I am even getting bored with it ;D ;D
So Mr Yamaha has let me down once again. I guess if you lived in FNQ you would understand. One of the best things about living here is the relaxed lifestyle. One of the worst things about living here is also the relaxed lifestyle. It doesn't matter if it has to come from Perth or next door it's going to take 2 weeks. Even in Maccas you usually have to wait for a burger.
Sooo sorry folks it's going to be next week. Hopefully Hilly will still have enough facilties left to be able to run the video. I know he grows older by the minute. I'd have to say I was VERY impressed by his holeshot on his first day back racing after 25 years. Well done son 8)
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yeah, you should have seen the grin on his face that day, longer than the Newell Hwy :D
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I reckon he deserved that grin Hoony. I would be well chuffed if I had achieved the same. I watched his video the kids made and apart from the great shots of the shitty weather (sky) you have down there they got some beauties of Dad bolting out of the gates then letting everyone go past :D :D. The commentry was just great. As I said to Hilly at least you can count on your kids to stick up for you. :D I have never met Hilly, but can't wait to. We've had a few good conversations on the phone and he has picked up a bike for me. Nothing beats talking over a beer. I'm coming down for the superbikes next year, so maybe we could make an event of it :)
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soooo! any news on that 125 of yours its rather quiet , cant here it running yet. ;D ;D
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This week-end. FINALLY got the bits back from Mr Yamaha. At the last minute he checked the shaft on the impellor ($69) and it was worn too. "That'll be another 2 weeks mate" >:( Kicking myself now that I didn't buy one of those on Ebay a little while ago. I wonder who bought them ::) ;D ;D.
Monday for the video - If I can work out how to download. Otherwise photos.
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So an update... Went and picked up the motor this afternoon. It was all good until I looked at the bill....$530 :o :o :(. I was a little shocked to say the least. $180 for parts and $350 for labour. Sooo from now on I will have to do things myself (with your help of course). I'm a bit cranky 'cause that $350 could have gone into a resto >:(. Apparently the bike has just doubled in value (or at least the amount ot owes me has!!)
Anyway enough bitching.. on with the story.
Problems encountered - Crank has turned in Main bearing on rotor side, Primary drive key was missing :o :o (Item 17 on the cranshaft diagram for those with a parts book - thanks DJ ;) ) I could be wrong, but i think that will explain the teeth marks in the clutch basket.
New water pump seal and impellor also fitted. Hopefully I will be able to have $500 bucks worth of fun on her this week-end to set my mind at ease :-\.
At least we have progress.
While I was at Mr Yamaha he mentioned he had all this old NOS yamaha stuff out the back and he is retiring 21 December. I put him onto zedder so he could find what bikes the bits come from. He gave me first option on the bits when he gets the list together. Must have been the shocked look on my face when I read the bill ;D ;D ;D maybe he felt sorry for me.
So let me get the list and I'll see if there is anything useful on it. Anything i don't take will go on eBay. I'd rather give the good blokes on here a chop at the bits first. A few things he mentioned was NOS side cover for DT360A and some NOS barrels of unknown origin. I'll keep you posted.
YZ video coming to this channel soon. Stay tuned
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She's back together. It started and ran OK. Still a bit dodgy though. Have good circulation through the radiator that it didn't have before. Steering head now bypassed.
I couldn't ride it yesterday cause I broke the clip on the joiner link on the chain >:(. I think I've got a spare hanging around somewhere ::).
Pulled the carby apart again to check out the jet sizes. Found jet needle to be 6F16 (on the middle groove). Going by the manual it is supposed to be 6F21. Geez it shits me when people screw around with things. Can't tell what sizes the main and pilot jets are as I can't see anything written on them (even with my glasses on). I'm guessing this is part of the problem. Looks like a complete new set of jets, so I can be sure they are the right ones.
Hopefully I can fnd that other spare link and should be able to get that video for Hilly 8).
Down to the small stuff now. Looks like I just have to work on the jetting and it will all be good.
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This is all sounding good 250H, yeah change that needle, the 16 is quite different to the 21. The 16 will make it run very rich threw quarter to half throttle. And look at the neddle jet(the brass piece the neddle goes in), that can wear oval, so its a item you might want to renew.
Good luck and keep the info coming.
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I reckon you are bang on DJ. Just came in from riding around. Took some photos, but we have some "technical issues" on the video. I will post photos tomorrow. Went through 2 litres of fuel in 2 sessions. No sign of dying 8) 8) Once on the pipe she goes very well - does that mean the main jet is OK ? I think as you suggested ages ago the pilot jet is too small as she will only push start with the choke on. I had to push start my old GSXR1100 a few times, so a 125 is dead easy ;).
Anyway at least I can ride around and have some fun on her. I'll get the proper jets and maybe chuck the boost bottle and she should be sorted. Now to work on those brakes and suspension :-\.
Thanks everyone for all your help on this one. Photos tomorrow and video some time after that.
It's almost time to put this thread to bed 8)
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It's a Yamaha. Accept it and move on.
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I would say that someone has over compensated on the pilot jet because it was running rich on the needle so they have put a very small pilot jet in.
Funny that Magoo, it sounds like he is moving on and getting some laps in.
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yep its to rich , its up there with the 250 on the needle, i recommend going standard then working from there, try these guyshttp://www.mikunioz.com/ they will help if you know the jet size , read the site first so that you have a better understanding of what jets you require ;D ;D unreal its running ;D ;D . CHEERS BONEHEAD
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Remember I never said it was pretty. No action shots yet (the missus was busy with the kids).
Comes complete with leg burner exhaust, "el flippo" rear guard and super shorty (broken) levers. Also note FMX style front guard ;D ;D 'cause we all now how good these old girls are for FMX :-\. The body is as I bought it. Fugly but functional.
At least it goes well now and with a bit more fiddling should be spot on. As normal for a 125 it spends most of its time on the pipe anyway. Should give me reliable service for a while - "new" clutch, transmission, crank seals etc etc etc. just needs a tidy up and some new plastics and all good :).
(http://i202.photobucket.com/albums/aa49/tbarsby/H-JReduced.jpg)
(http://i202.photobucket.com/albums/aa49/tbarsby/h-j2.jpg).
Will post video as soon as I can.
THE END !!!!!!!!!!!!!!!!!!!!!!!!! 8) 8) 8)
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250H that looks like a '84 YZ125L pipe so the standard jetting may not be quite right. Probably more midrange orientated.
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Hey Tony the pipe thats on your bike in my shed will fit it's got YZ125J on it and it's in good nick
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DJ,
That would explain why the pipe doesn't fit very well and has a mounting bracket in the middle of nowhere. Seems to work Ok - mind you I have nothing to compare with. I think I will go with it for now and see what eBay brings about. I'll keep my eyes open.
Hilly,
I reckon that bike in your shed is complete enough for me to leave it in one piece. By what you tell me and the photos you have sent it should just be a matter of getting her going again and giving it a once over.
The "L" pipe is in good nick too. No dings at all. Wonder if anyone would want to swap a good L pipe for a good H/J pipe?
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Why not put a DG pipe on? I use one and the bike runs great with it. They are sold by Dirtoverstock on ebay(us).
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Good point DJ. I will definitely keep that in mind. I haven't really done too much research on the 125 yet (apart from how to get one going ;D), the 250 has been the priority (and is again now that I have something to ride). The 250 is going to be scmick 8).
The way my riding is so far I don't think the pipe will be the limiting factor ::) ;D so I'll run with the one I've got at the moment. Once I get the 250 finished I will have a decision to make about which one to hit next - 125H, 125H/J or 80H. Still a bit of work to do on the H/J to get her past the scrutineers. I'll need to do a bit more research on that to find out what is required. Mostly things like sprocket cover and levers etc. I can probably do that at the same time as working on the 250.
I'll have a look at dirt overstock and save them in my favourites for future reference. Thanks for the heads up.
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:'(
Guys
98 posts on a YZ that only goes for 5 minutes, whats the story here? Sheezzz!!! :-[
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well it is a Yamaha !
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Yammie riders have plenty of time to chat about them 'cause you can only ride them for about 5 minutes! :D ;)