Small Engines (Lawn Mowers, etc.): I have a craftsman 6.75 lawn..., air hammer, starter fluid

Question
I have a craftsman 6.75 lawn mower that I just had servived (carb cleaned new gas and spark plug) and just yesterday it started refusing to start.  It rund fine for about 20 seconds then shuts down.  I can get it to run after a few sgots of carb cleaner and starter fluid.

Also, I hit a stump and replaced the bent blade, but it keeps hitting something on the deck that I can't detect.  I rotate the blade and have taken a hammer to a part that was bent but it still hits something.

Thanks for your help.

Liam

Answer
Hi Liam,

I would look at the flywheel key.  They usually shear, sometimes only partially, after an impact.  This conditon might cause the stalling because the timing would be off.  It also might be causing the scraping.
 The flywheel is located under the recoil/cooling shroud. Its' bore is tapered and mates with the tapered crankshaft. The keyway in the flywheel and shaft
keeps it from spinning on the shaft.  A nut secures it.  The recommended way to remove a flywheel is to use a puller.  An alternative, is to tap on the crankshaft top, with a brass hammer or use the round punch on an air
hammer.   The flywheel will need to be held up and supported or upward pressure applied with 2 large prybars. (A 2 person job.) Care is needed so the flywheel doesn't crack or bend.  Also be careful to not mushroom over
the crankshaft top.  Replace the key.  Install the flywheel after cleaning the tapers and re-tighten the nut to 65 ft/lbs.
There is also the possibility of a bent or twisted crankshaft depending on the severity of the impact but usually the key just shears.  

Let me know how you make out.
Michael