Fatten the bottom and lean the top, Geistware. Do ground run tests to make sure its not too lean at idle with the blade as closed as possible. If the plug is black, and 75% of your mixture comes from the Main jet, its too rich. A rich top end will also cause the idle, where you are trying to set it, to appear rich, and you will be mistakenlyleaning the bottom to try to straighten it out.