This flywheel assembly mounts on the engine crankshaft of a gas-powered line trimmer and provides the rotational mass needed to keep the engine running smoothly between power strokes. It also drives the ignition system by passing magnets over the ignition coil to generate spark. Replace this flywheel if the engine has no spark, runs erratically, or if the flywheel is cracked, has damaged magnets, or a sheared keyway.