yz eats trans lube?

[tristan18au]

i own a 2000 modle yz125 and it use a fair bit of trans oil. at the moment i am using a semi synthetic (shell advanced) light weight gear box oil, there are no leaks any where on the bike. whats going on? and is this an ok oil to use?

 

[Vic]

The oil may be leaking into the crankcase, due to a bad right main bearing seal.

 

[helio]

Further to Vic reply you should has a blue smoke from silencer, right ?

 

[skhasky]

This drove me nuts forever! I have a 98 YZ-125 - sometimes I would go to ride and 1/3 of the oil was missing. Sometimes none was gone. I checked - no leaks anywhere. I swore the right seal was leaking, but there was no other sign of this. I literally pulled my hair out over this and was ready to tear my cases apart when... a wise mechanic showed me the light! First, YZ 125's do use some oil - get used to it. The seal on the right side of the case is a sliding type and does not seal perfectly (all dirt bikes are like this). Second - you would probably notice less of a loss using non-synthetic oil over semi or full synthetic. This is a tranny - the synth isn't getting you much here - save it for the engine. Also, make sure to check your engine when it is cold. Don't top it off cold and then check it for loss right after a ride when it is hot (or vice versa) - oil will expand and contract based on temperature. If it is losing 30-50cc a ride - don't worry about it. Just stay on top of the oil and have fun! If you lose more and start seeing blue smoke and your jetting seems way rich / you oil-foul plugs like crazy.... then you can suspect the right seal.

 

[tristan18au]

what else should i look for?
the bike is not burning the oil!

 

[tristan18au]

i dont think it is the crank seal, cos its not gulping it, but after sitting it does go down.
HELP!!!

 

[skhasky]

Tristan... I am going to try and save you a ton of aggrivation. Mine wasn't 'burning' it either. It WILL fluctuate with temp. If it is not coming out of the cases (leaking) the engine is burning it - just too little to notice in the exhaust or performance. It truly sounds like you are having the same problem I did. It's nothing to worry about. Just check it each time you ride and top off as needed. If it starts to go through a lot of oil - then you may need a seal, which is relatively easy to do on this bike.

 

[tristan18au]

how easy is the crank seal to do on this bike?

 

[skhasky]

Well - you don't need to split the cases! I don't think you need it, but... If you want specific instruction's PM me.

 

[Jaybird]

tristan,
I'm curious how you know you are loosing fluid? Are you measuring it when you remove it? Are you putting in what the mfg. recommends or just pouring in a liter?

 

[tristan18au]

im checking the oil level bolt but i have tilt the bike right over to get it to dribble out but it is ment to run out when level.
im pulling the bike down to do my ring tonight i will investigate some more.

 

[tristan18au]

please tell me how to replace the crank seal?