Originally Posted by vincent713
I currently have the 49cc, seems pretty slow, then again it's my first bike. I was curious how much more performance I would get vs the 66cc? Can I change the head into a 66cc?
Probably not. My first bike was a 49cc and I bought the 66cc head kit. It turns out that the flanges at the bottom of the head do not fit into the bottom end made for the 49cc, so there are subtle differences. I WAS able to upgrade the 49cc to a 55cc.
Interestingly enough my 55cc bike has a CNC carb on it and out performs my three other bikes, all of which have 66cc engines. Personally I write that off to the original motor just being well balanced to begin with due to "dumb luck."