Sheared Flywheel key

[Paul_B]

I think I sheared the flywheel key on my 16HP briggs single. The flywheel turns, but the crankshaft doesn't. How bad are these to fix and what causes it? I know I hadn't hit anything.

[MPH]

Hardest part should be pulling the engine from the tractor. Then remove the shroud, remove flywheel nut, pull flywheel, clean up any burrs and replace key. Most likely cause I can think of would be backfireing. Maybe killing the engine under full load like can be done with a snowblower.

[Roy]

Flywheel retaining nut not sufficiently tightened can also cause key to shear. Been there, done that.