Small Engines (Lawn Mowers, etc.): eager 1 lawn mower fly wheel, crank shaft, eager 1

Question
My 12 yr. old mower has run like a champ with only minimal tune-ups until this fall. I hit some large rocks in high grass, causing a sudden stop and now it won't start. I suspect the flywheel key may be sheared. Here's the question: If the key is sheared, will the flywheel move independently from the crank shaft? I have inspected the blade attachment - it is OK. What else do you recommend I check?

Answer
The flywheel key will not move independently but the orientation of the flywheel key to the flywheel magnets being changed (due to sheared key) will cause the ignition timing to be off.  Make sure you take the numbers from the engine in to get a new key as there may be different ones for that engine.  The only other thing you may want to check is that the crankshaft isn't bent.  Hope this helps.