Re: Trying to figure out if it's worth it
A lot of places claim "150MPG" or "up to 150MPG" on those kits, but that's not realistic, from my experience.
I've had 5 66cc kits and they've all averaged 80-90MPG. Granted, I'm 6'4" 230 or so in tennis shoes, but I also pedal a lot under 30.
If you want that engine to last at 30-35MPH, you need a tall gear (36T or less) and the ability to pedal up to 10MPH or so before you let the clutch out.