Have you ever heard motor run? The plastic gear do wear out, and there's reasons why, and since the cover and flywheel will need to come off to replace the starter make sure flywheel key is not damaged, have a full charged battery, no gas in cylinders and all flywheel teeth are there valves are adjusted right. These engines are just about as good as they get. If you don't have the tool to replace ring gear just purchase a new starter with only the correct starter. Feed back your fix.