YZ250 Tranny/

[chillrich]

My 98 YZ250 was working fine until this afternoon, I noticed a hard shift between 2nd and 3rd then I thought I heard a grinding noise. Took the bike into the pits and all seemed fine with a visual inspection. When I returned to the track I found that the bike would no longer shift from 2nd. Finally when I got it down to 1st thats where it stayed. The shift lever does not move properly. Clutch does not disengage properly when the bike is not running.
My suspisions are that either a clutch piece has broken off and jammed in the shifter drum or a bent shift fork/shaft. I will be taking this apart real soon to take a closer look. Does anyone have any suggestions as to what the problem may be? Or perhaps which of these suspected faults may be more likely.

 

[spandy]

My guess would be it sounds internal. I would imagine you are going to have to split the case to find out.

 

[billtx]

There is a meachanism near the clutch that contains a ratchet, pawl, and spring. One of those parts may have broken. You can inspect it by taking the clutch cover off, it is at the other end of the shift lever. You don't have to plit the cases to fix.

 

[chillrich]

Thanx for the responses. I took a closer look yesterday afternoon and the external shift mechanism looks fine as well does the clutch and the shift drum( the shift drum shaft will not move even when the wheel is spinning). There was no debris in the tranny oil. A local mechanic will split the cases and repair it as I do not feel confident in taking on this procedure. He said the fault may be a shift fork, bearing or a gear(3 hours labour + parts).

 

[chillrich]

4th gear had a tooth broken off, 3rd gear dog was damaged, these parts will be replaced. I have been using ATF type F for gear oil, the clutch looks great but the mechanic indicated that there may not be enough rubber compound in this product to protect the tranny. Yamahas apparently don't use chromoly gears, KTMs and some others use chromoly gears in which case recomend ATF. The track is hard packed and landing jumps with the throttle on can be harsh. I will switch to Motul but am curious if this is necessary being a fairly conservative rider?

 

[KTA]

In my opinion changing oils isn't necessary, but no harm in trying a new oil. Are you the first owner of this bike? Having parts of a tranny wear out is not an uncommon issue (on an mx bike), regardless of tranny oil. My opinion is, if you change the oil frequently, it doesn't matter too much what you use, just keep it clean. Bad luck on it breaking, but glad you got it fixed up.

 

[JasonWho]

Thanks for the follow up. Sorry to hear of your gear and fork going out. Well, being broken, not going out like on a date. :-)

 

[KTA]

I think you may be in the wrong thread Jason. . . .haha.

 

[elf]

4th gear had a tooth broken off, 3rd gear dog was damaged, these parts will be replaced. I have been using ATF type F for gear oil, the clutch looks great but the mechanic indicated that there may not be enough rubber compound in this product to protect the tranny. Yamahas apparently don't use chromoly gears, KTMs and some others use chromoly gears in which case recomend ATF. The track is hard packed and landing jumps with the throttle on can be harsh. I will switch to Motul but am curious if this is necessary being a fairly conservative rider?

I had the same problem with my 00 yz250 except 4th and 5 gear broke, the dealer gave me a updated 4th gear. You could see the difference just by looking at it, one side of the gear was rounded off slightly. At the time I was using yamalube 20w50 so I really dont think it was your oil,also at the time I was mostly play riding, not riding hard at all.