Small Engines (Lawn Mowers, etc.): lawn mower starts and stops after hitting stone, air hammer, person job

Question
hi,

thanks in advance for answering my question.
my lawn mower has trouble starting every time.  now it starts and almost immediately, it stops.  this happened after hitting a large stone in the yard.
how can i fix it?

thanks.

dm


Answer
Hi Daniel,

I suspect a partially sheared flywheel key, which is common after striking an object with the blade.  Another symptom is the engine trying to pull back the recoil rope out of your fingers.
To replace the key, you will need to remove the recoil/cooling shroud to access the flywheel.  Remove the flywheel nut.  The flywheel is tapered and mates with the tapered crankshaft. The keyway in the flywheel and shaft keeps it from spinning on the shaft.  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 prybars or large screwdrivers. (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.


Let me know how you make out.
Michael