Small Engines (Lawn Mowers, etc.): lawnmower repair, impact gun, locking pin

Question
I hit a rock while cutting grass.  I think the locking pin? broke.   The blade doesn't turn when I pull the recoil.  What's involved with fixing it?

Answer
Remove the spark plug before working on the mower.

With the spark plug removed, tilt the mower with the spark plug hole facing up, and have someone pull the string to check for a bent crankshaft.  If the shaft or blade appears to wobble then the shaft is bent and the is probably not worth repairing.

Remove the blade and blade adapter.  Check for crank wobble again.  Inspect the blade adapter and key or keyway for cracks.  If everything is alright then you should check the flywheel key.

You will have to remove the top engine sheet metal or starter to gain access to the flywheel nut.  Remove the flywheel nut, an air impact gun makes removing the nut easy.

The keyway in the crankshaft and flywheel should be lined up.  If the key is sheared you will have to remove the flywheel and replace the key.  You will need some special tools to remove the flywheel.

Let me know what you find.
Eric