Small Engines (Lawn Mowers, etc.): Cant get started!, air hammer, person job

Question
I have a Craftsman 6.75 that is about 3 years old.  I attempted to cut my lawn the other day but unfortuatly hit a rock!  Since then I have not been able to get my mower started.  I changed the blade and the spark plug.  The lawn mower sounds as if it wants to start but I get no results!  Do you have any suggestions as to what might be the problem?  Thank you so much!

Answer
Hi Brandy,

Since it quit right after striking an object, I could almost guarantee that the flywheel key is sheared.  The timing would then be off.  The flywheel is located under the recoil/cooling shroud. Its' bore is tapered and mates with the tapered crankshaft. The keyway in the flywheel and shaft keeps it from spinning on the shaft.  A nut secures it.  Use an impact wrench on the nut or a strap on the flywheel.  Don't put force on the cooling fins or they will break.  The recommended way to remove a flywheel is to use a puller.   An alternative, is to tap on the crankshaft top, with a brass hammer or use a punch tip on an air hammer.   The flywheel will need to be held up and supported or upward pressure applied with 2 large prybars. (A 2 person job.) Care is needed so the flywheel doesn't crack or bend.  Also be careful to not mushroom over
the crankshaft top.  Replace the key.  Install the flywheel after cleaning the tapers and re-tighten the nut to 65 ft/lbs.
There is also the possibility of a bent or twisted crankshaft depending on the severity of the impact but usually the key just shears.  

If you have the work done at a shop you can expect about a $50 charge.

Let me know how you make out.
Michael