Does the whole clutch spin on the end of the engine? If so, then try a new clutch bolt for the clutch.
The taper is what actually locks on the clutch, not the bolt, you can actually take the bolt out once seated, but it is not recomended.
If the clutch is still coming off the taper, then the torque spec needs to be double checked, and inspect the end of the crank for marring that would not allot a proper seat on the taper.
If all checks OK, check crankshaft runout on the PTO end, and check TDC with a timing wheel on the engine, there may be a chance the engine is out of balance and is shaking the clutch off.
The taper is what actually locks on the clutch, not the bolt, you can actually take the bolt out once seated, but it is not recomended.
If the clutch is still coming off the taper, then the torque spec needs to be double checked, and inspect the end of the crank for marring that would not allot a proper seat on the taper.
If all checks OK, check crankshaft runout on the PTO end, and check TDC with a timing wheel on the engine, there may be a chance the engine is out of balance and is shaking the clutch off.