Ford clapper starter probs found
The starter was found to have lost its contact which is operated by the 'clapper' armature. As a result, the contact continued to work but poorly as tension was reduced and only the copper was touching together and burning. This caused the pinion to not throw forward as positively as it should, causing damage to the lead-in teeth area on the pinion.
The contact set is rivetted and welded to the coil (one of the field windings)lead, so a stainless steel round-head bolt and nut (about 1/8") was used. The starter worked again after replacing the drive-pinion and clutch assembly ($65,..ouch!).