Ifffffffffff the crank is on the correct spline and ifffffffffffff the cam is correctly timed to the crankshaft, when the Flywheels Left Hand Impulse Timing Mark (LHI) is at 3 o clock by the timing mark on the tractors side, the left piston will be at TDC and (if govenor is timed correct to cam) the open female slot in govenor shaft end (where mag mates) will be flat horizontal fore n aft.........
Soooooo get the left piston to TDC and see if the Flywheels LHI mark is at 3 o clock!!!!!!!!!!! If so the flywheels on the correct crank spline
If the clutch drive disk is on the wrong spline (or the flywheel on wrong spline on crank) ITS VIBRATION CITY....The heavy purposeful offset on the flywheel MUST BE 180 OPPOSITE from the heavy offset side over on the clutch drive disk. HAS THE CLUTCH DISK BEEN REMOVED AND WAS IT PUT BACK ON THE RIGHT SPLINE???Look for a V mark on the disk or insure its heavy side is 180 opposite from flywheels heavy offset
Maybe there will be other opinions??? or others can add to this, but thats my best shot