Correct me if I'm WRONG, I can take it!!
EXACTLY what IS a locked STARTER??
Here's my take on it, starting with TOO much ADVANCE causes the engine to turn backwards, propelling the starter gear backwards & winds it TIGHTER on the spiral & winds the Bendix spring, tighter than a DRUM!! THEN, EVERYTHING from the starter back plate on down to the spring retainer on the end of the shaft is loaded with TREMENDOUS HORIZONTAL PRESSURE & the starter gear CAN'T UN-WIND ITSELF ON THE SPIRAL & release itself from the flywheel! THEN, you gotta' push it in gear, to turn the motor FORWARD, to propel the starter gear, to get it traveling back down the spiral!!
There are many MIS-CONCEPTIONS about what goes on. Some even "think" it is gear teeth, climbing on top of other gear teeth????????????
(Sorry this is so LOOOONG, it took me 27 minutes to tipe it!)
Bill W.