Ralph..........getta new "clutch" style bendix drive. Yer old 'uns shot. The clutch style hangs in there longer while yer crankin'.
'Course ya could try cleaning the bendix drive. NEVER greese or oil bendix drives. Greese turns into stickum and slows down the starter gear insertion into the flywheel starter ring and makes 'em grind.
Heres the deal. The bendix screw retracts due to change in velocity. When your engine just koffs 1 sparkle worth, that makes the flywheel ring go just a little faster than the starter motor is turning and oops there goes the retractor spring.
Ideally, the starter motor should turn faster when the flywheel turns a little faster from just a 1 sparkie cauff. Starter motor may be draggin a little bitt from bad bearings so check them too. Because of the long starter shaft behind the flywheel bendix design, I always replace the starter bendix if I haffta do any starter motor stuff.
You will want to grind the starter hole a little bitt (1/4") at about 1-2 o'clock for eazier installation of the starter. Doesn't weaken anything and starter motor covers it up and nobody sees it.
When removing the starter motor, have a couple of 5/16 NC nuts to put on the very long screws so the starter doesn't fall apart. Brushes are a b*tch to put back in their holder...........Dell