Hmmmm- - - -this one's getting interesting. While you've got it apart this time, use a piece of emery cloth and give the commutator a good shoeshine-motion cleanup. Look for any evidence of burned spots at the edge of some of the commutator bars indicating you might have a shorted winding or more. Also look for evidence of melted solder where the windings meet the commutator. Any telltale signs like that make the starter a good candidate for replacement.
Once it's reassembled, you can bench-test each part individually. Connect one heavy wire from a battery to the small start terminal, and touch the ground wire to the connector between the solenoid and the starter motor. This will pull the solenoid in and check the operation of the drive gear assembly without turning the starter motor. Then connect a set of jumper cables, one to the big top terminal and the other to the starter housing, and short across to the start terminal with a screwdriver. This shold cycle the solenoid and run the motor. If it does all this on the bench, you've got a good starter!
Jerry
