Give the starter housing a couple of moderately firm taps with a hammer back near the brush holders- - - -the opposite end from the stomp linkage. It sounds like it's time for a brush and bushing job on the starter. If the brushes are worn down to a nub, sometimes a little massage with a BFH will coax a few more starts out of it. It's an band-aid, not a permanent fix.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!