This step-by-step riding mower repair guide explains how to replace the flywheel key on a riding lawn mower or lawn tractor. The flywheel key is a small rectangular piece of metal that keeps the crankshaft and flywheel aligned when you tighten the flywheel nut. To protect expensive engine components from damage, the flywheel key shears off if the mower blade hits an object hard enough to make the flywheel slip out of alignment with the crankshaft. Replace a broken or sheared flywheel key using a manufacturer-approved lawn mower part.
These repair steps show how to replace the flywheel key on common Briggs & Stratton engines used in Craftsman, Husqvarna, Toro, MTD, Murray, Cub Cadet, Troybilt and Ariens riding mowers and lawn tractors.