I´ve did 54 mph on my ZX this week. It was a nice tall hill and I had a nice 45-50 mph start on a good flat surface. One´s elevation may help as well, as I´m in the North Texas area. 45 to 50 mph on a good half mile length is what it takes my scooter to move my 180 body to its higher speeds. Derestricting a ZX-50 entails of replace one washer in the cvt with another style of washer and then clipping a specific colored wire connected to the cdi unit. The process can be found in your local Kymco dealer book.