I have a new Grasshopper 725G2 with 20 hours on it and the engine spits and sputters after about 2 hours of operation. Anyone bump up against that? The dealer said its a wet distributor cap from power washing but I haven't washed it since last fall. Dealer said to put new plugs in it. Should I expect the dealer to pay for that since its new and under warranty? Maybe give them the receipt?