I have a 2000 400EX that runs great but will not go into third gear. Its been like this since I bought it a few months ago. All other gears work fine, chain and sprockets are in good shape and adjusted per the manual. I've tried some clutch adjustment but it makes no difference.
When I shift from second to third I let off the throttle, pull the clutch in, lift my foot on the shifter and hold, and let the clutch out. As soon as I let the clutch lever out, even if I do it slow, the shift lever pops down on my foot and it sounds like it goes into neutral then back into second gear.
I've done some research and it seems like either the fork is bent or the third gear dogs on the gear are worn/ damaged. I was going to pull the side cover and inspect the clutch and the star behind the clutch for damage. I've read that these can cause the problem too but I'm doubtful. If I remove the side cover will I need to replace the gasket? Use honda only gasket?
If I pull the engine and split the case, what will I need minimum to change regardless of what I find wrong with the transmission?