The cause could be just from a worn gear that has started slipping and took the teeth off. Inspect the ring gear on the flywheel for broken or chipped teeth, and also make sure the ring gear isn't cracked. Other than that you may just need to replace the plastic gear. Some of the older engines had plastic flywheel ring gears that were prone to tooth damage, and can be replaced with an aluminum gear.
Thank you for your reply. I forgot to mention that the starter was new.It striped the old gear down,so i set the valve lash to 4tho.
installed new starter spun well for a while then it seemed like it had too much compression again,took off park plug and turned engine over again then noticed gear was flat.Today I installed new gear and it did well so far.
Never worked on the tractor starter gears, but there is usually a gear tooth engagement spec. I remember a 1/8" drill shank test on GM stuff . Just a comment.
