Small Engines (Lawn Mowers, etc.): Honda Lawnmower vibration, honda lawnmower, mounting bolt

Question
My Honda Lawnmower HRS216PDC, engine GCV160 was being used to mulch leaves when the user hit a stump and the mower stopped.  It continues to start easily but now has an obvious vibration.  The blade has no bend to the eye.  Is it likely that the crankshaft is bent or are there other, hopefully less catastrophic, causes for the problem?

Answer
 Hello Charlie:

 Sorry for the Delay. Remove the Spark Plug. Tilt the Mower so the Plug Hole is Up. Carefully Turn the Engine and Watch the Blade Mounting Bolt. Does the Bolt Turn True or Does it Wobble when the Engine is Turned? If the Answer is Yes it Wobbles, then the Crankshaft is Bent. If the Answer is No it Doesn't Wobble, then the Blade is Bent or Off Balance. Hope this Helps. I am here if you Require more Assistance. Let me know what Happens, Please. Thanks.

 Good Luck

 Respectfully

 John