What's the year, make and model of the garden tractor that you're dealing with? If it's the Craftsman DGT6000, did it develope this problem since you recently put the snowblower assembly on the tractor? It sound like a electrical wire has schaffed or been pinched to ground causing a short that...
Your problem might possibly be fuel leaking into the cylinders due to a worn needle and seat in the carb, allowing fuel to perculate into the intake manifold.. Short of replacing the carb, you could put an inline fuel shut-off valve in the fuel line and make sure you turn it off whenever you...