Snapper 1855A, 18 horsie Onan. Eng runs good, sometimes hard to start. I have replaced the fuel pump with an elec. pump. New plugs, coil, cleaned the carb and repaired the exhaust muffler. It runs great, but sometimes going along it starts to stutter, moving throttle to idle for a second usually takes care of it. After clearing the stutter it runs good for a while. Sometimes a couple minutes, sometimes 30-40 minutes then does it again. I also replaced the fuel line and installed an inline gravity flow fuel filter which is staying clean. I had the tank off/empty and cleaned it out good.