[bmc]

Had this problem before as well. Found that the ring gear was working its way ever so slightly off the flywheel in spots where the starter bendix was making contact. 6v starter now using 12v causes one hell of a push/pull with the starter. Removed starter and inspection plate and the ring gear needs to be flush with the flywheel. I had to tap where they come together with a brass hammer in a couple spots while turning the engine over by hand. I would never have known about this until someone pointed it out.