I'd pull the stator cover and check the flywheel, see if anything is amiss in there.

If the woodruff key sheared and the flywheel moved, the timing would be off and it would be popping and/or backfiring so I don't think it's that.

Lots of vibration is usually related to the clutch gears not being aligned with the 3 marks when reassembled.

If it's minor vibration it could be loose, broken, or missing mount bolts or **** frame.