Runs properly on propane, will only run on gas till choke starts to come off. This has been going on for about 5 years, now it is my turn for a kick at the can. The cylinder head had been redone, the carb replaced, managed to get my hands on the original carb and found the choke had been secured partially closed, someone came to same resolve as me and cheated to keep it running. My vacuum is good with no leaks, removed the manifolds to check for carbon build up, minimal deposits. Timing is on,new plugs, wires, rotor and cap. Yes this customer wants it to run on gas and very seldom wants to run on propane.