Tractor was running fine, what little I have ran it until yesterday. I started it to get it ready to cut my field and what I thought was oil but turned out to be water mixed with carbon (soot) from within the exhaust pushed out around the muffler connection and ran down over the carb and side of the engine and started to skip then stalled and has not fired since. I haven't taken time to do anything other than check the fire( which it has) and the oil which is new and still clean, coolant level is also good. The tractor has a newer muffler with a rain cap. My best guess is head gasket problems but not knowing anything about these engines I'm looking for any input as to what can cause this to occur when not running, I had the tractor running the day before and it ran fine. The engine spins over freely but does not fire off. Any help here would be appreciated.