[davidimurray]

Look at the HP rating of the bike you are planning to uses. Generally they are all pretty much the same excpet for the diameter. I am going to use ZX6R carbs on my 1.8 pinto as they should be good for around 110hp. As strange as it sounds go for the smallest you can for the hp you want. The bigger you go the worse the throttle response will be. While that doesn't really matter for a track car it makes a big difference on the road for the sake of 1 or 2 bhp.