Ok, I haven't been here in a while, but I came and asked some questions before building my first motorized bicycle using the Grubee Skyhawk 66cc angle fire engine kit. And it worked out great! I've put over 2500 miles on it using it as a daily commuter and for shuffling around town. Now I have a few questions before attempting to enhance my build on my next bike. First, I used the basic setup, on a single speed Kona Unit mountain bike with 2.125 inch tires, and was able to hold a steady speed of about 35 mph, topping out around 38. This was a blast for a while, but now I want to go faster My main questions are about my options to get more speed out of my next build. If I were to simply use a smaller 36 tooth sprocket on the rear wheel as aposed to the standard one, how much faster should that get me? My father also said that I could make the front sprocket in the engine a bit larger, not only helping my top end speed but helping to keep my chain better in place, has anyone done this? Also, I've been considering moving to a multispeed bicycle and finding a jackshaft kit. I'm not too familliar with how they work, but I may try moving up to one of those also. If anyone is using one and can give me feedback I would appreciate it.