Red Haired Girl Posing With The Motorbike

Until World War I, the largest motorcycle manufacturer in the world was Indian, producing over 20,000 bikes per year. By 1920, this honour went to Harley-Davidson, with their motorcycles being sold by dealers in 67 countries. By the late 1920s or early 1930s, DKW took over as the largest manufacturer.
After World War II, the BSA Group became the largest producer of motorcycles in the world, producing up to 75,000 bikes per year in the 1950s. The German company NSU held the position of largest manufacturer from 1955 until the 1970s.
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 NSU riders in the 1954–1956 seasons, they abandoned further development and quit Grand Prix motorcycle racing. Moto Guzzi produced competitive race machines, and by 1957 nearly all the Grand Prix races were being won by streamlined machines. The following year, 1958, full enclosure fairings were banned from racing by the FIM in the light of the safety concerns.
From the 1960s through the 1990s, small two-stroke motorcycles were popular worldwide, partly as a result of East German Walter Kaaden's engine work in the 1950s.