The GX610, 18hp V-Twin engine on my 'new' (800 hours) TW6 died if gas was < 1/2 full, then if < 3/4 full, and now will only run for 2 seconds if gas is dumped directly into the carb. I checked fuel filter, fuel pump, fuel lines, fuel cut-off solenoid, and fuel quality:confused2:. Anyone have...