The 50 cc class was the ultra-lightweight class in Grand Prix motorcycle racing, and formed part of the Fédération Internationale de Motocyclisme (FIM) World Championships from 1962 until 1983; when the class was replaced by 80 cc.
Read more about 50 Cc: History and Development of The Class, The 1961 Coupe D’Europe, World Championship Status, The Japanese Withdraw, 50 Cc GP World Champions