The carb has been set to about 12 lbs of pressure which is about 1 1/4 turns. It does have black smoke and the plugs are black. I just replaced all the plugs and reduced the jet size. The carb only has 500 miles on it so I don't think it's a bad carb. My theory is maybe a bad fuel pump that is increasing pressure?? Also, the tires are suppose to be brand new put on a month ago.