Re: Huffy Good Vibrations Cruiser mod
40MPH is not that hard to achieve but why would you want to do it? These are bicycles, not motorcycles. Bikes are designed and built for moderate speeds. 40 isn't realistic, or prudent when you're talking about a bicycle. You're dealing with bicycle wheels, frame, brakes and bearings. They weren't meant for sustained high speeds.
As I said, it can be done and it doesn't require gears or a shift kit. It doesn't even need to be a highly modified engine but my advice is to rethink your goals. You'll be safer.
Age and Treachery Will Always Triumph
Over Youth and Skill & "Charlie Don't Ride"