How many hrs? Unit may have intake issues with build up of carbon. Also ignition parts replaced? Next is fuel. Vaporizer drained? Has to be hot. Plug on lower right corner on bottom. If it hasn't been maintained replace vaporizer. Also any inline fuel filter. There's been a lot of dirty propane coming thru. Next is inch pedal adjustment. Look at cable action ontop of trans. Make sure it's all the way released. And slack in cable. Like 1/8 inch. If not adjust it to have this. One way to check proper fuel is to sit on unit, start engine and hold tilt lever either way on. Then step accelerator pedal down fully. If your rpm increases to nearly full rpm your fuel system and ignition should be good. Check also that your mixer is tight on manifold and all 3 gaskets are good. Usually every 5000 hrs need repair to ensure a good seal.