I have a 2001 48" Lesco walk behind. Has been running well but Monday started to run rough out of the blue. Turned it on and off and let it sit and eventually it started to run okay. Changed the fuel filter today and checked the spark plugs - they looked fine. Ran it again today and it ran okay for a few minutes and then started to run rough again. It sounds almost as if it's going to die but then keeps going but is very rough sounding and there is a gasoline smell. I finally just shut it down. Is this a carburetor issue and/or fuel pump? I'd prefer to buy the parts and fix myself if possible rather than pay to get it fixed. Any ideas?