Small Engines (Lawn Mowers, etc.): Lawn mower vibrations, craftsman lawn mower, crank shaft

Question
I have a Craftsman lawn mower model 917.377110 model.At one time I mowed on and tall grass not seeing a big 2/3 inch  wood branch = the mower stopped and checked to see the branch was stuck. I was able to take out the branch.When I started the mower again , I noticed more intense vibrations.Thinking that the blade is bent, I ordered and replaced the blade(using the same part number)I started the mower and still the mower vibrates( maybe less but still there is thatunsual vibrations). I cheecked the blade  for wobble by using a fixed reference point or spot at the metal housing. Rotating the blade - both points or ends of the blade lands or passes reference spot.
Am I doing the correct way to check for wobble. How do you check if you have a bent crank shaft. Can you suggest what other source/s causes vibrationns.
Thank you .

Very truly yours,
Joe Reyes

Answer
 Hello Joe:

 Remove the Spark Plug. Remove the Blade. Replace the Blade Bolt about 4 Turns. Turn the Engine and Watch the Blade Bolt Head. Does it Wobble? If so then the Crankshaft is Bent. Hope this Helps. Let me know what Happens, Please.

 Good Luck

 Respectfully

 John