Ever had a Chrysler starter apart, ever rebuild one? Stator, armature, brushes, bushings or bearings at either end of the stator, maybe a relay wih contacts needing cleaning. Most DC motors are similar in construction. You got nothing to lose. Sand the contacts on the stator, clean the spaces between them, brushes can made or bought. Clean all the dust out, oil the bushings/bearings, etc. If you can rebuild a carb you can do a dc motor. Take pictures as it comes apart and have at it. Or an alternator/starter rebuild shop might tackle it.