http://www.simpsonmotorbikes.com/55cc Hop up Kit.html
I know I don't really care actually. The use of gears makes small engines way more efficient in all regards. As I said in my other post there is a solution on the way however that should be available by the time, if that time ever comes, that the current laws become enforced. It will not be cheap though.
I feel that a mature operator can utilize gearing to enhance their motor assist experience along with the proper cc engine, meaning 49cc or less, and keeping their top end gearing to 30 mph. The biggest benefit of gearing is the low end anyway for most of our needs and the ability to get off the line efficiently and cruise without being all wound out on the top end is just to good to not do it.
Quite frankly most of the bikes and various contraptions I see on here with folks bragging about how fast they can go, up to 50 even, scares the beejeezus out of me. Save it for the racetrack boys, there are ambulances on call there and you may stand a chance.
YOMV of course.