Yea, I'd like to know too, when switching to Race Fuel, what is a typical rejetting? Down on the main like Yamaha thumper asked?One of the common features of contemporary racing fuels is oxygenation. Not all have it, but about half do. This means that in addition to the air coming through the carb, part of the mass of the fuel itself is oxygen in a form that becomes free to take part in the combustion process. To compensate, you have to add more fuel, which means richer jetting.