My yardman mv20s with kolher engine only starts when I put gas in carb. And turns right off. Cleaned out the fuel lines from carb to tank and bowl at carb.. has spark on plugs wires.

Have you checked out your float, sounds like the float may be stuck in the up position. If not sure how to do this just write back and we'll help from there

This has a mechanical fuel pump .you might check that.

Also, is there a wire going to the underside of the bowl? If so then that needs to be checked. I installed one once abd did not know it had to click into place, thought it just slid on. Wrong, had to click so my slid off after a month and ran just like yours.

Sounds exactly like a bad fuel pump.