I have a three year old L118 with a 20HP Briggs and Stratton engine on my John Deere Lawnmower. It ran fine in early November. I just changed the oil and the air filter and now when I tried to start it, it just turns over but will not start. It finally wore my battery down. Since it turns over but does not start, I suspect something may be wrong with the fuel system. The tank had a little gas left in from last November. In the past, I never had a problem leaving the gas over the three month winter period. I did not use a stablizer. Do you think I could just buy some new gas and fill the tank with new gas? Or do I need to put a new fuel filter on and spray something like a carb cleaner in the fuel lines? I am looking for something easy to do that will get it started. Thanks.