I have a John Deere JS46 about 3 yrs. old. It has an awful miss and emits black smoke. There seems to be a lot of black carbon buildup in exhaust. Took out Champion spark plug, it was black, replaced it with an NGK. seems a little better but not much. Wondering if I need to clean carb because gas with ethanol may have some buildup inside. I left it running and ran a tank and one half of fuel through it. Anyone have any ideas?
