Well I think you got an incorrect model number posted based the type and trim codes. It is either a 28M707-1130-E1 or it is 28N777-1130-E1.
First You don't never, never strike a permanent magnet starter motor. It is a sure way damaging the motor by breaking the magnets or knocking them loose. Plus that L-head engine not really all that old being that is a 2001 engine; although, might be depending on your age.
Now the starter may worn out brushes or bushing wise causing the starter to drag but as said beating on the motor is only going to damage it farther. THis thought is because the engine spins freely when the plug out so there shouldn't be a valve binding.
Now it could also be a worn camshaft lobe as the camshaft has automatic compression ramp or bump ground on one of the camshaft lobes.
