They actually race those crazy things in France . . . they soup 'em up somehow but are required to keep 'em at 49cc. The engine is good for about 1 race. Anyhoo, they can hit 60mph . . . that's 97 kph (yeah, it does sound faster).
Mark my have to links to videos of some of those races. It's funny to see those guys on those racing Solexes, lying flat on their belly with legs sticking straight out the back!!
Smiff