I have an FH580V 19 HP Kawasaki with 550 hours on it and it sputters when you put a load on the engine. Only does it when its hot. I've kept up with the valves adjustment since new. I've only run synthetic oil in it. Keep the filter clean. New plugs. New fuel filter.I tightened up the air gap on the coils to .012" from .014 to see if that would help, but had no effect.. Engine does not burn oil. Starts and runs fine for about 30 mins. then starts to sputter under a load. If anyone has had this problem and can shed some light on it, I would appreciate it.