The ring gear in a Briggs and Stratton engine is located under the flywheel. When the ignition key is engaged, the current from the battery is transferred to the starter. This engages the gear from the starter against the ring gear, turning the engine over. The original ring gear is plastic; under the heat of the engine it becomes brittle, and the teeth from the ring gear can begin to break off. Replacing the ring takes some knowledge of engine theory.
Place the engine on a flat work bench. Remove the rotating screen screwed onto the top of the flywheel.
Remove the blower housing covering the top of the engine using the socket set.
Place the flywheel holder on the fan retainer that's bolted to the top of the flywheel. Remove the flywheel nut with a 30mm socket and wrench.
Remove the two screws that hold the fan retainer and fan in place. Install the flywheel puller. Turn the puller screws into the flywheel puller holes evenly.Tighten screws equally until the flywheel breaks free. Remove the flywheel.
Turn the flywheel over exposing the ring gear. Drill out the rivets holding the gear in place. Pull the gear off.
Install the new ring gear, in the new ring gear kit are small screws and nuts to hold the gear against the flywheel. Tighten down screws.
Slide on the flywheel, screw on the fan and fan retainer. Bolt on the flywheel, reinstall blower housing and rotating screen
The replacement gear comes as a kit, and can be purchased in either plastic or aluminium, even though the aluminium ring gear more expensive, it has twice the lifespan and worth the extra money.