Tecumseh Lawnmower Repair: Removing flywheel, replacing timing key and re-installation. Mower with a sheared timing key, usually caused by mowing rocks or debris. (happens when blade hits immovable object) Symptoms can be: Hard to start with backfiring, pull on cord and yanks back (ouch) or runs and sounds strange. Not the best video but good information. Lawn mower repair at The Alameda Repair Shop, Alameda, California 94501