Picked up a John Deere JS28 Push mower last year. This year it fouls plugs terribly and burns fuel like crazy. Not very impressed with a one year old mower, but what can I do. I've checked the carb and don't see any kind of adjustment on it. How come it starts running rich all the sudden? I can't even finish mowing my back yard (small yard) without filling up again and cleaning the plug. Anyone have advice?