Small Engines (Lawn Mowers, etc.): Possible bent shaft on craftsman mower, craftsman 917, seal gasket

Question
Hi Eric,

I have a Craftsman (917.387620 - 6hp B&S) mower - probably on it's fourth or fifth season.  I struck a good sized rock that was substantial enough to stop the motor.  I tried to restart it and it shook like a wet dog.  Thinking it was just the blade out of balance, I put on a new one.  It immediately started the same thing, striking the deck and shearing the blade adapter.

My question is, am I looking at a bent shaft?  It doesn't appear bent, and I'm not getting any leakage from the seal.  It was starting easily, but now its even difficult to pull the starting rope -- kind of lurching.

I'm guessing I should look in to a mower.  If so, is this one a complete goner, or is it something I could rebuild as a backup.

Answer
To check for a bent shaft, remove the spark plug.  Have an assistant tilt the mower with the handle touching the ground.  Have the assistant pull the string while you watch the shaft.  If the shaft or blade appears to wobble then the shaft is bent.

As for rebuilding, it may not be worth it.  New engines can be purchased for almost the price of a crankshaft, gasket and seal.  The last shaft I bought cost about $80.00...new engine $150.00.  Add the cost of the seal, gasket, blade adapter plus your time and the price comes out about even.

Let me know if the shaft is not bent.
Eric