The early 1930s found Zundapp struggling at just 5% of the market share and with little in the way of exciting products. Their engineering prowess was well established however, as Zundapp collaborated with Ferdinand Porsche on some volkswagen designs that would later influence the Beetle. The answer to the product dilemma was the K series. This was an all new platform that would serve for models from 200cc up to 800cc. The K series was launched in 1933, and the K800 was the flagship model.
K stood for Kardanantrieb which basically described the drive train. It was a Cardan shaft drive, which was mated to a four speed hand-shift gearbox. The gearbox was in turn mated to a horizontally opposed four cyliner engine that generated about 27hp initially. The first K800 measured 797cc in displacement which grew to 804cc by 1938. The drive train is attributed to engineer/designer Richard Kuchen. The K series included a number of novel ideas at the time including enclosed shaft drive, a unique "strainer" oil filtration system, enclosed crankcase, etc. Front suspension was a girder fork with a single spring, while the rear was rigid without suspension.
The bikes were beautiful in their design. Pressed steel frames were similar to the BMWs of that era, but the lines and the finishes for both frame and engine were an elegant and complementary combination. This is particularly true of the interface between the fuel tank and the frame, but it also extended to the two-tone fishtail exhaust, and the "ears" for the headlight bucket. Even the vents/intakes for the engine complemented the design. Floor boards were provided for both rider and passenger. In the end, the K series had the desired effect, boosting Zundapp's market share to 18% by 1939. The basic configuration would inspire that of Honda's Goldwing 40 years later. It was also a platform which generated some memorable machines at the time besides the K800 (see The Green Elephant) Having seen one up close at the Barber Museum, you can see why it is considered one of the great designs of the last century.