While plowing snow today by tractor quite suddenly back fired and stalled and would not restart. I noticed a fair bit of snow melting off the block so I assumed the ignition may have gotten wet. I came back to it about half an hour later and it restarted and I headed back to the garage. However it starting running rough after a couple of minutes and again backfired, but not as loud, and stalled and again wouldn't restart. Is the problem wet ignition? if so, what should I do about it? If not, what might the problem be?