There have been a number of aftermarket options over the years. In times past there have variety such as . . .Mikuni smoothbores (29mm typically), Weber (and other brands) dual carb setups, single carb or FI /log manifold setups typcially for turborcharger use and Keihin CR racing carbs. For new stuff today, Cycleex offers a dual carb setup (webers?) that sort of fits in the stock frame, and updated Keihin CRs are a available. Search under Keihin CR for more info . . .
