I have a Craftsman LT2000 18hp OHV. Went to start it up and when the starter gear engaged the fly wheel it made a odd noise and the starter gear snapped off the rod. Upon inspection discovered the starter motor was missing a mounting bolt and was loose. Thought the gear had engaged the fly wheel at a bad angle and caused the break. I replaced the gear and secured the starter motor. When I cranked it up the starter gear broke off the rod again!
I assume something else is wrong. Any suggestions before I install a new starter motor?

Inspect flywheel assembly, and alignment. Can you turn the engine by hand?

Thanks for the response. Yes, the fly wheel does turn and feels like compression is good, haven't yet cracked open the valve casing to check.

Assuming OEM parts, and it's not an alignment problem (starter gear position, starter motor foundation?), then yeah shafts, valves, and pistons may be indicated. How do you know it seems to be getting good compression? Got a manual, contact number for the manufacturer?

It just occurred to me to first check your starter solenoid wire(s) to the battery to confirm proper engagement, AND disengagement. Please keep us updated.