Small Engines (Lawn Mowers, etc.): Toro B&S OHV GTS 140 mower-bent blade, now clanks, air impact wrench, excessive vibration

Question
Hi. Today I hit a stump and bent the mower blade and now my 22 year old mower starts to vibrate heavily and clanks and I immediately turn it off. I would like to see if I need to replace the flywheel key but if I do do I need to somehow adjust the ignition timing afterwards? The repair manual for this mower says that the ignition timing is not adjustable. If the key is sheared is replacement all that is needed for it to run smoothly again?

Thanks in advance.

Answer
First thing I would check the crankshaft.  REMOVE the SPARK PLUG before working on the mower.

Have a helper raise the mower by stepping on the handle.  While the helper is standing on the handle have them pull the string and see if the crankshaft wobbles.  If the shaft appears to wobble it is bent.  Make sure you do not mistake a bent blade for a bent shaft.  Bent shafts will cause excessive vibration and can eventually destroy the entire mower.  

If the shaft is staight then you need to check the flywheel key.  Remove the external parts to gain access to the flywheel nut.  Remove the flywheel nut and use the correct flywheel puller to remove the flywheel and inspect the key.  Replace the key if necessary and re-assemble.  FYI, we use an air impact wrench to remove the flywheel nut.  An electric impact usually will work as well.  However, make sure to use a torque wrench when re-installing the flywheel nut.

Please send me the mower model number located on the Toro sticker.  The stickers are usually on the rear portion of the deck but I have seen them under the bagger door and even under some handles.  I can look up all the parts if i have the five digit model number.

Eric