YZ125G Build

[alexbrown64]

Just want to give a plug out to motoretro. These guys have a big range of nos parts for a variety of vmx bikes, are based in Oz, and are pretty cheap with great postal rates.

I have picked up the rear chain guides, air box lid retainer, nos gaskets and even a new 6f34 needle that I have been after for ages.

Check them out at motoretro.com.au

[alexbrown64]

Sunday arvo and i said to the boy, lets go out and get the G running for the first time. We stripped and cleaned the carby. It was full of muck, main jet blocked and airbox was full of fluff. The G has been sitting for years and years.

Put fresh fuel in the tank, checked for spark, put new oil in the tranny, pulled the airbox off, as its full of disintegrated foam and muck.. and then kicked it in the guts.  The lad had control of the throttle, as i have pulled the housing apart.
 
Started second kick and sounded great... 30 second vid of the big day.....

https://youtu.be/8oxKaOLPIHU

Next is to get the throttle back together, whack the seat on and run it through the gears up the street like a hoon....hopefully there are no problems..
Then she can finally be pulled down for her rebuild.

Cheers,

[ITDOG]

Too lovely, I have the IT175H always thought it would be nice to get the long legs off the 125 and dress her with the yellow plastics from the US model and run the yz higher revving pipe. Your young fella loves it eh

[alexbrown64]

The boy loves it ITDOG.  He has his own toys though.  A 1979 RM80N that we are still trying to get running.. a JR80, and a 73 silver tank XR75 that we are rebuilding and he wants to ride at some VMX meets.

Cheers,

[alexbrown64]

Well, it was like Mad Max on my street today.

I cobbled the G together, bits hanging out everywhere, no seat cover or side plates, overalls on, no helmet..... started first kick, no choke, and idled perfectly. Took her up the street... she rips!! it was pulling wheelies just from the torque in the powerband.  Ran through all the gears perfectly.
Only downside was there was no clutch.  Looks adjusted right, actuator goes in, but no clutch at all.  This is only a minor, as after sitting all these years the plates are probably all stuck together.  I will look at it in the rebuild.

So... time to strip her down, clean the frame up and weld up the small rusty bits... then off to the powder coaters on her long road back to glory..

Cheers,

[skypig]

Although it is extra work, there is some advantage to finishing the project before powder coating the frame. Then stripping it back down and getting it done.

It's a little heart braking to find you need to weld, heat, grind, or drill, something during assembly if it's freshly coated.

[alexbrown64]

Thanks Skypig.  Im hearing ya, but im also impatient.  I did notice the frame needed some adjustment to make the rear guard sit right.  I have also noticed some rust holes.  I tested a spot with a wire buff.  Eats the rust and takes it back to bare metal in seconds.  I am going to wire wheel the entire frame back to polished bare metal, repair all holes, check it thoroughly and then get it done.  Cant remember, but does powder coating cover small pits in the steel. I may be able to flap disc them out, but i think my powder coater uses a high build primer.

Last pic of the old girl before she gets the tear down....



I now have most parts to begin the rebuild.  Its going to be a long slow process but should be good fun.
Below is a pic of the decals i have collected.. rim, rear guard, fork leg, tank and side covers.. plus some stencils for the original seatcover made by Stencilmaster.  I have included the airbox lid retainer as an example of the nos parts i have been collecting... lots of goodies.. plus i now have a mig, plastic welder, zinc coating and anodizing kit.
Tim Lee made the shock decal and it is an exact replica down to the serial number of my shock! The rear manufacture decal has been date stamped as well.



Progress pics as i go.  Feel free to nit pick as i am aiming for bike as close to the showroom floor as possible. Although i want to use as many of the original parts from this bike as possible.  Pipe will be off to Pipe King for the treatment soon...

Cheers

[alexbrown64]

Hit a major hickup last night.

Stripped the bike down and the last bolt, which was the swingarm pivot/engine mounting bolt was seized solid. No amount of pounding would move it. It would not even turn.
Got the heavy ammo out this morning and used a 1/2 drive air rattle gun, an electric Hilti set to hammer, dremmel, a propane torch and a can of penetrant.
Took a while but the constant heat, electric hammer, rattle gun and lube finally broke it free.. but had to sacrifice the pivot bolt (mushroomed bolt ground back down with dremmel).



I got stuck into it with a wire buff to remove all the rust and check out the weld and any cracks etc..
Come up pretty well..



Cool frame number...



The frame is about 90% good. No missing tabs, all original, good steel etc.. but the 10% is terrible.  The gussets in the seat rails have rust holes... and there is some pitting in some areas of the frame and one small hole in a down tube.... repair time...



I may have to replate the gussets, use my mig to fill one or two holes, flap disc out the pits, use rainex to transform the rust inside the tubes and then when i am happy.. it will be off to the powder coaters..

Cheers,

[alexbrown64]

I cut out the rust from the frame and welded in some new plate to the gussets. Tig would of been good to zip it all up, but i only have my mig...



I had the original front number plate with the bands that strap it to the forks.  However, the white surround had perished while the black number plate and mount system was good. If you could ever find one, they can run up to $700.  I decided to transplant my original black plate into a DC replica G plate.  It worked out well.  Made it an interference fit with the dremel, file and lots of time. Once cleaned up, i used the Selleys 2 pack plastic glue that is made for polyethylene and polypropylene.



Its not finished yet.  I still have to mold the top of the plate so it fits around the bars. Then the front of the plate will need prepping and painting sating black taking the black out a bit further to the edge so that the white border is not so large.





Cheers,

[alexbrown64]

Perfect fathers day... got up and tinkered on my bikes.. daughter came out with a cup of coffee.. now kids are making me bacon and eggs..

I trimmed the rare front number plate some more and am about 50% through working on it.  I am happy with the progress on it.  Will still need some sanding and polishing, and then i am thinking of getting some vinyl ovals made up with my old original race number.  There is a mob out there whereby you give them the exact measurements of you ovals top/bottom side/side and they will make them with personalized numbers, borders etc.. I think that would be pretty cool for my old G.

I have also been working on the original seat cover.  Used a vinyl repair kit to fix a couple of minor nicks in the cover.  For the seat base, i am going to use bicycle cloth stick on rim tap to put an edge around the edge so that it doesn't cut into the vinyl again.

[Woody]

Nice job on the plate Alex. Your F is going to look great with the work your putting into it.

[alexbrown64]

Cheers Woody.

Has to go on the backburner for a few weeks but have some big plans for her in the next few months. I have just stripped the shock down and have ordered a new seal head and bump stop. All parts are just about ready for powdercoating.

Cheers,

[alexbrown64]

Have been in contact with Geoff at GMC. There may be a chance of a YZ125G GMC cone pipe. At the moment it's just a concept. Geoff does an It175g/h pipe. The 80/81 It175 shares the same frame and engine (albeit modified) as the yz125g. Geoff's pipe for the It is tuned for enduro work. The concept is to adapt it for MX.
I will be sending lots of pics and measurements, but does anyone have a G near his place in Broadford for final checks?
Otherwise I may have to do final cuts/mods and tig tacks and that would mean sending the pipe back and forth.
I will be sending my Oem yz125g pipe with all clearances marked out to help Geoff with fitment and design.

Cheers,

[OverTheHill]

Sorry, not been following this but looks like it's been going on for a while. Loved my old [new] G, probably was the pic of them at the time & had mine on Alky [methanol] & certainly performed well. The one & only [stupid] problem that sticks out is when the rear end stayed down & bugger me i'd tightened the axle so much [& so many times in a year or two] that the spacer swelled enough to stop the floating brake from 'floating' therefore the plate couldn't rotate even the small amount required to counteract suspension movement. You would think maybe end float was taken up from squashing washers end on many times but 'no' it actually expanded the sleeve through the plate so an adjustable reamer & all good--just not on the day!!. Yours look great i must say.

[alexbrown64]

Thanks overthehill, i will keep an eye on the brake arm.

Just tinkering with things over the next few weeks.  Frame is nearly ready for powder coaters, but need to pop engine and pipe back in to get some measurements for GMC to get ready for a cone pipe.

I mucked around with the original seat cover so much and it still didnt look right. Decided to try a replica one from Pit Replica.  I got an RM80N one once, and it was perfect.  This one for  the G is really good too.
The grain, fit, logo size, position and correct font were all really good.
The base was in poor condition.  3 bolts snapped off in the threads, lots of rusty staples, dirt, grime etc.  I removed all the staples and bolts, tapped the threads, cleaned everything up and set about installing the cover over the original 3R3 seat foam and base.

I have an Arrow T50 stapler and it does the job quite well.  Have to really stretch the cover to get it to fit, and it still took over an hour to get it on.
Looks pretty good now, and i would say the seat is coming up around the 90% mark.  I will polish and re-zinc the seat mounts and she will all be good to go.





I think i have most of the parts now to do the G rebuild.  The shock seal head and bumper arrived the other day along with a bunch more parts. 
A bunch of stuff has to go to the powdercoaters and i have to prep and zinc a ton of stuff.  The shock will be going out for a rebuild, GMC is doing a pipe and silencer and i still have to repair and prep the plastics.

I have decided to deviate slightly from a full on OEM build and just have some slight changes.
I am leaning towards stripping the anodizing from the rims and polishing them up, together with re-zinced gold nipples and silver zinced spokes.
The GMC cone pipe will be polished and welds blued and then clear coated.
The OEM painted aluminium swingarm will be stripped, sanded, polished, then a grain added with a scotch brite and then clear coated.
The number plates are having my old race number and name on custom vinyl oval backgrounds.

Besides that, most everything else will be OEM, NOS or replica of original.

Cheers,