My JD l110 with a comand 17.5 hp engin made a loud bang and died . I tried restarting it but it would fire . I checked the plug and there was plenty for spark there was good copression plenty of fuel checked the valve train and every thing looked OK I tried either and it still won't fire once in a while it will back fire just once.

Hi,
Put in a new flywheel key. That is what happened at the same time as the bang; sheared the key. It will still have fire; just not at the right time.
Peace,
Clarke