1991 yz 125

[owain]

hi i am an owner of a 1991 yz 125.it has a few problems:
1.it leaks gearbox oil out of the exhaust and is usin way too much oil :|
2.the previous owner had taken off the expansion chamber and hadnt put the o-ring and metal washer back on.will this have an effect on the bikes power?
3.to pull away you have to give it a full handfull of trottle.can someone tell me why?
and im just wondering how hard fork seals are to change on these bikes?
thanks

 

[eagles22793]

gear box oil i dont think that is what it is 2 strokes do leak a little bit of oil out the exhaust if mixed riched not putting an o ring back in will not effect the bikes power it will just leak a little bit of exhaust handfull of throttle could be maybe a dirty carb try cleaning it good and changing fork seals is not hard but dose require some machincal skills to understand everything

 

[owain]

well mine leaks like mad and smokes like mad too.i think the pulling away is the clutch slippin or doin sumthing.
i have diagrams to do fork seals and it looks very confusin.
and now its misfiring with fresh prmix :@

 

[gary2010]

ur oil seals in the bottom end might be gone for the oil coming out the exhaust. my bike spits some black oil out from the oring and a little bit around the back side panel from spitting out the silencer but i thinks thats normal if u put abit 2 stroke in. get some new gaskits and oils seals for the bottom end i would change the main bearings while i was there to. i would check the woodruff key for the misfireing or just clean the carb out. yeah ur bike defo shudnt be losing engine oil

 

[owain]

woodruff key?whats that?
in the winter me nd my dad are going to strip the whole bike nd engine nd fix it wooooo:D
the right side panel(exhaust side)it always coverd in oil and the swingarm is also.
if the main jet was worn would it cause strange fuel use?

 

[gary2010]

theres a little moon shaped piece of metal sitting in the crankshaft that keeps the flywheel in place, it cases misfiring if this happens. you just slide the flywheel from the crankshaft then the woodruff key should be there.

its always the right side of my bike that gets oily from 2 stroke thats nothing to worry about well i wouldnt think so. but if ur losing the engine oil in the bottom end that is not good. behind ur front sproket there is an oil seal rub ur finger around there and see if the oils cumin from there, when mine went it would chuck loads of oil on the chain and the oil would spray up the rear mudgaurd and get all over the swing arm too it was a perfect straight line of oil on the bottom of my mudgaurd lol off the oil coming from the chain when i was driving it

 

[owain]

i think the oil seal in the engine is gone which means more going into the exhaust and then leakin out silelcer

 

[gary2010]

do you need to keep topping up the engine oil? can u see any oil on the floor after u leave ur bike for some time? you might be putting to much 2 stroke in, i was on my rm85 on the weekend and that was spluttering like mad and cutting out, i filled up with fresh petrol and less 2 stroke and it ran perfectly.

 

[Matt90GT]

right crank seal is out, thus you are loosing gearbox oil.

means you have to pull the motor and split the case to change it. Probably a really good idea as then you can inspect/replace the crank, piston, power valves and reeds.

when you reassemble the bike, clean the carb and air filter and run new gas at 32:1.

Once you have rebuilt the motor, you shouldnt have any power issues beyond being a 125. They dont have low end power.

forks are not hard to do, you just need the correct size seal drivers.

 

[owain]

wow thats a lot of info matt thanks.ill check that out in the winter.
gary i have to top it up every few weeks the isnt oil on the floor but there is all over the swinging arm+side panel.i sorted the boggin down the carb needed a clean.
can any1 tell me what jets they take?the main jet didnt have a number on it

 

[Matt90GT]

www.servicehonda.com

look up the parts fische. It will tell you the stock jets.

 

[owain]

found it thanks :cool:

 

[owain]

now its runnin waaaay to rich.im usin 50:1 fuel/oil mix and have never had any problems befor... HELP