SINCE IT EMIGRATED to China back in 1984, Zündapp has become the forgotten brand in Germany’s two-wheeled history book. Yet, after commencing bike production in 1922, it was for many years the country’s largest motorcycle manufacturer – albeit postwar in the Western half only – and as recently as 1977 produced as many as 115,000 bikes in a single year, before sales of its, by then, predominantly two-stroke range suddenly slumped in the face of Japanese competition, sending it, just seven years, later into the hands of the liquidator. But for more than six decades Zündapp was at the forefront of the German motorcycle industry, and it surely ranks alongside BSA, Norton, Indian, Moto Guzzi, Triumph, Gilera and Harley-Davidson, as well as its BMW rival, as one of the most…