[09crf450r144]

Runs fine looks mint and goes through 1-3 gears, but won’t shift into fourth or fifth.. ideas? I was thinking bent shift fork or shift drum. Maybe a head or two needing replaced but have any of you encountered this? It’s fine in 1/2/3 nothing for 4th and 5th and by nothing I mean it won’t go into those gears it’ll stay in 3rd. Advice ?