Still has the factory foot starter to the right of the throttle? If so not alot that can be the problem other than the starter drive (sometimes call a bendex but not technicaly correct. remove the starter and the drive pinion, should rotate on the armature shaft only in one direction (and have a slight drag). most likely yours is shot & will freewheel in either direction. If it makes a grind noise could be a worn flywheel ring gear as well.
