4th gear going out?

Hello all. When I'm going full speed wot in fourth gear on my 2003 yz450f it feels as if my clutch lever gets pulled and let back out real quick it does this about 4-5 times every ten seconds and gets worse as I reach the top of fourth gear... Someone told me that it was my main jet but I'm not for sure.. Any ideas??

Only does it in 4th?  You can make it stop by backing off the gas some?


The lugs on the sides of 3rd and 4th gears on the main shaft are worn out, and the front shift fork is bent because of it.

If I'm splitting the cases to fix this problem anyways. Could I throw a 03 wr450 transmission in it?

Yes you could.  The trans has to be from an '03-'06 WR450F, and it has to be complete, both shafts, shift cam and forks.

Ok thank you very much for you help. Where abouts would I find a wr450 trans.?

I'm going though the same bullshit with my 04 yz 450 I put a new crank in and rode it 5 times before 4th gear started slipping. Never again will I do a bottom end without doing the transmission

I narrowed it down to my clutch pressure bolt springs being loose causing my clutch to slip... Hope you find what's wrong with yours..

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