'01 426 Gearbox issue

My brothers just bought a second hand 2001 YZ426 and it seems to "jump out" of 5th gear. It happens anytime after shifting into top, it jumps out of gear resonably violently, the motor instantly free revs and then it re-engages. It continues this cycle till down shifting.

Has anyone else had / heard of this problem with the 426?

I've heard of problems with soft 4th gears, but it seems to me like an issue with the selector dog or pawl not holding engagement?

i dont have any, what the hecks he doing in 5th anyways!? :)

Could be a bent shift fork or that gear is just worn out..

What kinda riding did this guy do to be in 5th

DESERT ?

I have a problem with my 00 jumping out of gear, but that is my feet are to big and they keep hitting the freaking gear shift.

Freestyle does that meet with your approval or are you gonna spu something stupid again

Yes, jumping out of 5th is a very common problem on the Supermoto scene. The answer is apparently to have the gears back-cut..

It's usually intermittent though, if it happens every time, then maybe you have a bent selector or worn dogs?

I had this exact problem with my '99 WR400! I ended up pulling the engine out and stripping it down. I found that the dogs on 5th and 3rd matching gears were worn/rounded, but I believe this was caused by a bent center shift fork. I replaced the 5th and 3rd gears on the counter and main shafts (4 gears) and all 3 of the selectors. It was interesting to note that the new center selector was "beefed up" indicating to me that they are weak? Good luck and let me know what you find! :)

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