First off, I know very little about mechanical things. The tractor has 65 hours on it and has been starting and running great up until today. I started it up, let it warm up then drove it a short distance then turned the throttle to low and got off to grab my gloves. It started running rough, the valves seemed to get louder then it died and won't start at all. It turns over just fine but won't start. Any help would be appreciated.