1955–90: two-stroke motorcycles and mopeds
In 1955, the year that the Simson brand name was restored, the factory also began making two-stroke mopeds. The first model was the SR 1, a 48 cc machine producing 1.5 bhp. This was succeeded by the SR 2 in 1957 and the SR 2E in 1959. In 1958 Simson launched the KR 50, which has integral legshields and a rear wheel enclosure like a motor scooter, but 16 in wheels like a small motorcycle. The KR 50 had a 48cc motor like the SR-series, but with a higher compression ratio that increased power output to 2.1 bhp.
When four-stroke motorcycle production was terminated, the Simson factory was directed to concentrate on moped production. In 1963 it raised the KR 50's compression ratio to 8.5:1, which increased power to 2.3 bhp. In 1964 this model was succeeded by the KR 51 Schwalbe ("swallow"), in which the KR 50's 38 x 42mm long-stroke engine was revised with almost square dimensions of 39.5 x 40mm and 50cc displacement. Compression was raised again to 9.5:1, increasing power by almost 50% to 3.4 bhp. Moped production grew steadily in Suhl; up to 200,000 mopeds were built per year. In 1965 the Simson factory employed 4,000 workers.
In 1964 Simson launched the SR 4-1 Spatz ("sparrow") and SR 4-2 Star, each of which had motorcycle-style bodywork without the legshields and rear enclosure. The Spatz initially had the long-stroke 38 x 42mm engine and an 8.5:1 compression ratio and produced 2 bhp; the Star had an "over-square" 40 x 39.5 mm engine with 9.5:1 compression and produced 3.4 bhp. In 1967 the Spatz was revised as the SR 4-1 SK, which shared the Star's 40 x 39.5 mm engine dimensions but had an 8.5:1 compression ratio and produced 2.3 bhp. Spatz production was ended in 1970 and Star production was ended in 1975.
In 1966 Simson introduced the SR 4-3 Sperber ("Sparrowhawk"), with the same 50 cc engine but with power increased to 4.6 bhp and more angular styling than the Spatz and Star. In 1971 Simson introduced the SR 4-4 Habicht ("hawk"), which was cosmetically the same as the Habicht but had the same 3.4 bhp power output as the Star. Sperber production was ended in 1972 and Habicht production continued until 1975.
In 1968 Simson was merged with VEB Ernst-Thälmann-Werk Suhl to form the VEB Fahrzeug- und Jagdwaffenwerk Ernst Thälmann Suhl. The Schwalbe helped the company to worldwide fame, and in the DDR the scooter stood for the success of East German two-wheeler motor manufacturing. The Schwalbe was slowly developed over the years. In 1968 the KR 51/1 series was introduced with power increased to 3.6 bhp, followed in 1979 by the KR 51/2 series with 3.7 bhp. Schwalbe production was ended in 1986 in favour of more modern Simson 50cc moped models.
In 1970 Simson introduced a bicycle-style, pedal-start moped, the 50cc, 1.6 bhp SL 1 Mofa. Mofa is a contraction of Motor-Fahrrad, German for "moped". The model was revised as the SL 1S in 1971 but was discontinued in 1972.
In 1975 Simson revised its image with a new model, the S 50. This used the 40 x 39.5 cc version of the Simson engine, produced 3.6 bhp and was produced in various versions until 1980. Its successor was the S 51, in which Simson revised the styling again and returned to a long-stroke engine, this time with 38 x 44 mm dimensions and a 3.7 bhp output. The S 51 was built in various forms until production was ended in 1990.
In 1983 Simson introduced a 70 cc model, the S 70. This had the S 51's long-stroke engine bored out by 7 mm, giving over-square dimensions of 45 x 44 mm and producing 5.6 bhp. Like the S 51, the S 70 was produced in various forms until 1990.
In 1986 Simson introduced a new 50 cc scooter, the SR 50. It had legshields and unlike the KR 50 and KR 51 it had scooter-sized 12 in wheels. However, it had a motorcycle-style rear mudguard instead of a scoter-style rear enclosure. In 1987 a 70 cc version, the SR 80 was added to the range. The SR 50 and SR 80 were made in various versions until 1990.
