I'm very happy with my 70cc. Does 50 mph on the flats (thats all we have in Delaware) before it's starts to 4 cycle or rev limit. I cant tell which, but it doesn't
If you've got a biturbo and a good carb setup, I would say try putting in a 27 tooth
sprocket. It's good for a little extra top end and may accomplish the same feel as
the trans shift change you want to do. Plus, it's cheap.