You would have to be missing at least two adjacent flywheel teeth to keep the drive from engaging, and you'd never get more than one turn of the engine before it set up a horrendous grinding noise, or stopped turning. The copper washer is no longer reversible- - - -only one side has a copper coating on an otherwise steel washer. That change has been incorporated into solenoids for at least 15 years, maybe longer. Don't know what you'll do with the burned contacts in the end cap, as they're not reversible any more, either.
It sounds like the one-way clutch in the starter drive is slipping occasionally. if you decide to repair the starter instead of installing a rebuilt unit, do it right, with new brushes, machine the armature, change the front and rear bushings, new solenoid linkage, install a new or rebuilt solenoid, and a new starter drive. You'll only pay about 50% more than a good rebuilt starter will cost that way, and be sure to charge out your labor time at about $5.00 per hour!
Jerry
