OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Engines Questions On Briggs & Stratton Engines Briggs and stratton 12hp keyway sheared

I've had some difficulty seeing the tiny starter motor bearings being able to generate enough resistance to shear the keys Joe, but the key point seems to be that the "wrong" side of the keyway was damaged. It seems to be the side that would get mashed if the flywheel stopped and the crankshaft kept going, or if the crankshaft were suddenly accelerated relative to the flywheel. It would be easily explained if some kind of wedge dropped in between the outside of the flywheel and some stationary part of the engine, or between the flywheel ring gear and the engine, but Mick is sure that kind of thing didn't happen.

Edit: I'm wondering now if maybe the flywheel isn't fitting down onto the taper. It might be the wrong flywheel? If it doesn't sit on the taper, the key could easily be sheared on the side where the keyway damage is. That would be due to the engine always starting on full throttle, due to the way the governor operates. With a full throttle start and a loose flywheel, the crankshaft will rotate faster than the flywheel does and thump the key from the left side. It will keep on thumping the left side of the key every firing stroke, until the zinc key gives out - which might be quite a few thumps, but that would only take a very few seconds. It could even damage the keyway, by the time you'd done it over and over again with new keys.

I'm really looking forward to finding out what has actually been happening.