Help gear shift

[twinshocks]

I have a 2001 KX250 that jumps out of fourth gear when under load. Have removed right side cover and all seem to be fine. Would welcome any advice as to what may rectify the problem.

 

[RM_guy]

Sounds like it could be a worn shifting fork or less likely a worn gear. Sorry but the only way to tell is to split the cases. Probably not a bad idea anyway for a bike that's 21 years old. Seals and or bearings my need replacing too.