Here's a 50cc (count them, 50cc, model aeroplane engines can be bigger than that) Kreidler Grand Prix bike. The manufacturers used to loiter round schools looking for lightweight riders, and once contracted, they were not allowed to eat for the whole season, and had to keep their fingernails REAL short! http://www.vintagebike.co.uk/Bike D...2 H - M/pages/Kreidler-50cc-VanVeenRacer2.htm (Back then there were 5 classes in GP racing; 50cc, 125cc, 250cc, 350cc and 500cc.) This bike is probably from the early 70's. And while you're there, hop over and have a listen to the 1965 Yamaha 125 SOUND file!!