Small Engines (Lawn Mowers, etc.): Problem with Craftsman Lawn Mower, crankshaft, crankcase

Question
Hello John,

Thanks for the help. I changed the blade and it did help reduce the vibrations, but the vibrations are not gone completely. What else can I try? How do I check for the bent crankshaft? And if that is the problem, how do I fix it? Please let me know. Thanks for the help.

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Followup To

Question -
I have a Craftsman 6.75 HP 21" Lawnmower, model # 917.378922. While mowing, the blade hit the edge of the Patio and stopped immediately. On restarting, the mower started vibrating vigorously and it sounds wierd. I tried starting again and it starts but it shakes a lot and sounds odd. What could be the problem? Please help me determine the problem and fix it. I still have a portion of the lawn that I need to mow!

Answer -
 Hello Sid:

 1- Check for a Bent Blade. If Replacing the Bent Blade Helps but there is Stiil a Vibration. Let me Know and I will Help you Check for a Bent Crankshaft. Hope this Helps.

 Good Luck

 Respectfully

 John

Answer
 Hello Sid:

 It will take 2 People to do the Crankshaft Check. 1- Remove the Spark Plug. 2- Tilt the Mower Towards the Plug Opening and Remove the Blade. *Always Tilt a Mower Towards the Spark Plug. This Prevents Oil from Getting into the Crankcase Vent and Filling it with Oil.* 3- Replace the Blade Bolt (Just a few turns is all that is required). 4- Have Someone turn the Engine While you Watch the Blade Bolt. If it Wobbles, then the Crankshaft is Bent. From your Earlier Email and from what you have said this time; I feel you will need to take this Mower to a Shop to have the Crankshaft Straightened. Hope this Helps.

 Good Luck

 Respectfully

 John