Check for a bent blade. If the blade is jammed on the mower chassis, check that the engine crankshaft does not rotate off center (remove plug lead, pull in PC handle, and pull starter whilst watching shaft). If crank IS bent, drop me a line for a cheap replacement engine.
If shaft is straight, replace or straighten blade, and attempt to start. If engine kicks back, check flywheel key.
phil_saunders@bigfoot.com
Phil Saunders, November 2008