Very important now is too install the gearchangeselector plate correctly and adjust it properly. After assembling move the selector arm and while changing gears up (rotating the selector anti-clockwise!) make sure that the shifterpawls just rest on the curved point of the pawl plate and not further. Any further and the gearbox might jam solid! In the Yamaha manual is mentioned 1 mm clearance, but this is incorrect.

You can see on this picture that the upper pawl is just (safe) on the plate. That is the way to adjust the setting bolts.