Motorcycle a three-speed gearbox and belt transmission. It was so popular with its users that it was nicknamed the "Trusty Triumph." By 1920, Harley-Davidson was the largest manufacturer, with their motorcycles being sold by dealers in 67 countries. In the 1950s, streamlining began to play an increasing part in the development of racing motorcycles and the "dustbin fairing" held out the possibility of radical changes to motorcycle design. NSU and Moto Guzzi were in the vanguard of this development, both producing very radical designs well ahead of their time. NSU produced the most advanced design, but after the deaths of four
Motorcycle racing 1200 cc for twins, and between 750 cc and 1000 cc for four cylinder machines. The motorcycles must maintain the same profile as their roadgoing counterparts. The overall appearance, seen from the front, rear and sides, must correspond to that of the bike homologated for use on public roads even though the mechanical elements of the machine have been modified. Supersport racing is another category of motorcycle road racing that employs modified production motorcycles. To be eligible for Supersport racing, a motorcycle must have a four-stroke engine of between 400 and 600 cc for four-cylinder machines, and between 600 and