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01 yz 125 build thread.

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Hey there, so I bought a 01 yz 125. I was told it ran but rough, I get to his house, and it doesn't run at all, he attempted to do a rebuild by himself, but then stuck it back together. The bad by just looking at it:

-radiator is bashed in

- plastics are cracked

-spark plug is black

- forks are leaking

-shifter is bent

- clutch cable is messed up he said

- seat is torn

- air filter is non existent

- brake is pretty bad

- sprockets and chain are worn

Good:

-the other half of the rad is good

-that's it

I'll start by tearing it down, get the engine sorted out, and then suspension and lastly looks.

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EXCELLENT!!!

Yup. Should be a fun time, I have a few other projects going right now( eagle talon, yj jeep, etc), but I hope to get to it ASAP. Maybe a week or 2.

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EBAY:

GPI radiators-82.00

Plastics-120.00 

Graphics-60 to 200 your choice

Piston kit, lower end, or complete top and bottom-81,180.00, or 260 to 300.00

RMATV/MC:

Lenexx muffler packing (good stuff)

And for all your other odds-ends

 

Suspension rebuild:

your choice-"local"

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EBAY:

GPI radiators-82.00

Plastics-120.00

Graphics-60 to 200 your choice

Piston kit, lower end, or complete top and bottom-81,180.00, or 260 to 300.00

RMATV/MC:

Lenexx muffler packing (good stuff)

And for all your other odds-ends

Suspension rebuild:

your choice-"local"

Wow thanks. 1 of my priorities is to get it running, then worry about plastics and such. I know you've heard this a million times but what sort of company should i go with for a piston? Sleeve vs no sleeve? I'll do the research , but just asking for personal experience. Also, do I need to get both sides of the radiator? Or just one. Do they come in separate peaces? Or is a hoes all what's connecting them?

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Langcourt.com will replate and supply the piston if you like, or buy one and send it with jug. If you have no way of measuring it, just buy from them so it is perfect. They are in Canada also. Sleeves are steel and runs hotter than nikisil. You can get one radiator if you want, but 82 for both sides is hard to beat. Three bolts to frame and hoses hold them together.

I prefer Vertex Pistons, wiseco, hot rods, OEM if you have the money for crank. There are companies on eBay that mix and match. Also, stick with OEM bearings on the crank if you get into the bottom end.

You can PM and we can talk off line also.

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Big update, I tore the bike apart, and such. The only problem I have is with removing the rear wheel, the doesn't seem to disconnect, I Tried prying the brake apart from the disk, no luck. Also, I found a inscribing that says you have to add a 2mm washer, I'm guessing to the spark plug hole. Also, I think he also installed the piston the wrong way, cause the arrow is pointing towards the intake/ air filter.

Some pics ImageUploadedByThumper Talk1440178004.942714.jpgImageUploadedByThumper Talk1440178023.691931.jpgImageUploadedByThumper Talk1440178059.230302.jpgImageUploadedByThumper Talk1440178088.697308.jpgImageUploadedByThumper Talk1440178151.700474.jpg

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Sweet...

 

Put/spray some penitrating oil on the axle bolt and then get a long large bolt that you can hammer and push it through. 

 

Head may have been shaved so much that the dome of the piston hits pug. What does the inside of hear look like?

 

Yes, piston is facing wrong way. 

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Sweet...

Put/spray some penitrating oil on the axle bolt and then get a long large bolt that you can hammer and push it through.

Head may have been shaved so much that the dome of the piston hits pug. What does the inside of hear look like?

Yes, piston is facing wrong way.

Inside of the head looks pretty good, I don't know what to really look for though, I'll post of a pic. Now I'm at a crossroads...

1. Should I flip the piston and see if that fixes the problem of it not running at all?if I do, what's all involved in removing the cylinder(idk really what to call it), there's 4/5 nuts holding it down if I remember correctly. Is that all that's to it? Do I have to do anything else so that it comes off easily? Pic of what I'm talking about below.

ImageUploadedByThumper Talk1440197968.430847.jpg

2. Should I go ahead and tear the motor out,and check the crank/seals.

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1. In order to remove the cylinder you must remove the nuts holding it on. Also, the power valve linkage arm thing will need to be detached from the power valve shaft. you have to remove the power valve linkage arm cover on the right side of the cylinder and it will be pretty straight forward from there. Just remove the screw holding the arm on the shaft and pull it off.

 

2. It's definitely a good idea to check the condition of the engine internals. If the piston was put in backwards who knows what else might be wrong with it.

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You don't need to pull motor out of frame to do seals. As described, you will need to pull the jug/cylinder by 4 base nuts, power valve linkage cover, power valve linkage bolt.

With the piston backwards, true... Who knows what else was done wrong.

New head and base gaskets while you are getting seals.

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Ok ,thanks for all the replies. Decided to pull the engine , as there was only 4 bolts holding it in, and also because my crank case oil was basically gas. Now I'm thinking maybe it was something before the engine? That was dumping excessive amounts of fuel. The reeds look fine, no chips anywhere. I haven't looked at the carb yet, but I will do so too. The piston has what looks to be a crack/dent in it, which(guessing here) let blow by and shoved gas down through the intake on the piston( it's the wrong way round) which then made it down to the crank. I drained most of the gas from the crank area, and now I'm wondering where to either

1. Blow it out with compressed air and hope any left over doesn't ignite.

2. Take it apart,new seals, same crank, and clean it to get all the gas in the pores and case.

3. New crank, new seals, and check the rest of the engine; clutch, stator etc.

Edited by joeyschmo101
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Crank is either very lightly rusted either from the exposure to air(no oil On it), or burnt due to thinning of oil by the gas and such.

ImageUploadedByThumper Talk1440307886.679105.jpg

Crack on the piston I was talking about.

ImageUploadedByThumper Talk1440308057.242782.jpg

ImageUploadedByThumper Talk1440308155.534057.jpg

Edited by joeyschmo101
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Piston needs to be replaced, ring got caught and now I think the jug has the witness marks of that. (replte needed)

 

Crank color is fine and as long as there is no crunching sound don't pull case apart, just clean it out real good with compressed air and fuel oil mix.

 

Head looks like it could be shaved a little, but still not enough to warrent a extra plug gasket. (hard to see from pics.)

 

Engine seal kit

Engine gasket kit

Piston

Re-plate jug

And you should be good on the motor.

 

 

EDIT: Did you get the axle out?

Edited by PALMER84ONE

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Piston needs to be replaced, ring got caught and now I think the jug has the witness marks of that. (replte needed)

Crank color is fine and as long as there is no crunching sound don't pull case apart, just clean it out real good with compressed air and fuel oil mix.

Head looks like it could be shaved a little, but still not enough to warrent a extra plug gasket. (hard to see from pics.)

Engine seal kit

Engine gasket kit

Piston

Re-plate jug

And you should be good on the motor.

EDIT: Did you get the axle out?

Ok sounds good. Yes I got the axle bolt out, it's just I still need it for the triangular stand. I bought a parts washer, for future projects and this. I'll report on it to see if it's worth the 100.

For anybody else doing a first time rebuild, kroil all the bolts possible, makes them much easier to take out. Take pictures, and work backwards to the engine.

For washing out the crankcase, can I just run the old oil straight through it to catch all the gas, and then put new stuff in? How do I know which size piston to put in after its honed? I'm guessing I should just take it to Machine shop ?

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