i can run close to 40 mph on a 44 t rear but only at high rpms for short bursts, the way to get there is a good port and polish, high comp... decking the jug and head and using a head with a good squish, a tunned pipe or strait pipe tunned length for the rpm your running at, and a well tunned carb.
the cns carb is an awsome carb if you tune it right, i am running the cns v1 and its awsome !
the easy way to go faster is to change gearing it can make all the differance in the world ! just going from a 44 to a 36 will make you feel a differance, the only reason i keep the 44 is cause i love the torque and i can go faster with more rpms at the cost of motor life