1st remove the spark plug and then ground spark plug wire to the engine for
safety reasons. Then turn the mower over with
the carburetor in the up position and check the blade and crankshaft for damage.
The blade will then need to be removed and check the crankshaft by looking at
the end of the crank shaft as someone pulls
the engine over. Check for any wobble in the crankshaft. If the crankshaft is
bent you will need a new one or some times
you can get that one straightened. I don't recommend to straighten them because
sometimes they will crack and may break off later.
If the crankshaft is OK then you will probably need to replace the blade with a
straight, balanced blade. Also check the
blade adapter to be sure the key is good and there is no damage to it. Reinstall
the blade before trying to start the motor.
If the motor still will not start or recoil rope jerks out of your hand then you
will need to check the flywheel key.
To learn how to replace fly wheel key go to
www.lawnmowerman.com