Try rolling the bike backwards and forwards with the engine off while trying to shift the gears. It should shift through all the gears. If not, the problem is a broke shifter pawl. If it does, the clutch is not releasing properly.
The shifter pawl can be replaced fairly simply. The clutch is a different story. If the clutch is dragging, you need to determine exactly why it's not releasing. Bad cable, not adjusted correctly. Good Luck!
Answers & Comments
Try rolling the bike backwards and forwards with the engine off while trying to shift the gears. It should shift through all the gears. If not, the problem is a broke shifter pawl. If it does, the clutch is not releasing properly.
The shifter pawl can be replaced fairly simply. The clutch is a different story. If the clutch is dragging, you need to determine exactly why it's not releasing. Bad cable, not adjusted correctly. Good Luck!