ORIGINAL: BudBud

Did you try adding a little fuel to the mixture? These engines seem require a richer fuel mixture than some others. They do not do well at all when they are too lean. I agree with Tib on the non-insulated carburetors, but that should not be causing this problem. Where I see them acting up is once the engine is hot, they can be very hard to start. The fuel boils back away from the carburetor in the fuel line. I like the way these engines tune and hold a tune, but like I said, I find they need a little richer fuel mixture than others. Stammering, cutting out, unusual leaps in idle or low end rpm variations, all can be attributed to lean conditions. It might be perfect today and too lean tomorrow. Temperature, elevation and humidity affect these more than most people realize. I would also check the fuel lines for anything loose or cracked. You could also have a glow plug on its last leg, but normally I get a couple of gallons out of the stock SH plugs. Glen