Re: 49cc vs 66cc
I put a CNC Carb on it too. Then I replaced the crappy air filter that comes with the CNC carb with a K&N one. It also has one of the newer exhausts on it, the EPA certified ones, which I believe are less restrictive.
This sits on an Electra Coaster 7 frame which is a longer frame then usual and provides additional space for the carb and air filter.
Unfortunately I've had problems with the rear wheel warping on this bike since it has been using the old "rag joint" method of holding the drive gear to the wheel. I think that between that and the increased performance this engine seems to have the spokes (even heavy duty ones) can't hold up with me and my son's use (read abuse) of it. Currently it's down for repairs to the wheels. I have two other bikes that work fine, however.