1939 DKW SS 350 LADEPUMPE: LOOKS ARE DECEIVING
Looks are deceiving in the case of the 1939 DKW SS 350. Upon starting this graceful looking German piece of engineering it turns into an evil sounding violent shaking beast of a motorcycle. Even today the ‘Ladepumpe’ DKWs are remembered as some of the loudest machines that were ever raced. DKW’s water-cooled forced-induction twin-piston two-stroke engine has four pistons, two each with a common combustion chamber, fed by a counter-rotating and double-acting charge pump or ‘Ladepumpe’. The SS 350 is essentially a supercharged two-stroke.
The basic principle of a split-piston engine is to separate the intake and exhaust ports by using two distinct cylinders with their own pistons, rising and falling in unison and sharing a common combustion chamber. The intake ports are cut into one cylinder, the exhaust ports into the other. The added ‘Ladepumpe’ is a separate cylinder with piston mounted at 90 degrees to the main cylinders which compresses and forces the fuel mixture before combustion.
The SS 350 produced around 32 horsepower and was capable of a top speed of 165 kilometers per hour. DKW had a silver paint scheme for its factory racers and a red-and-black one for privateer machines. This privateer SS 350 is virtually identical to the works ‘UL’ machines, meaning it has the 180 degree placement of the Ladepumpe cylinders. It is also similar to the bike that won the 1939 German and European championships as well as the last important pre-war race, the 1939 Grand Prix of Germany.
Before the war DKW employed around 7.000 people in Zschopau in what was at the time the largest motorcycle factory in the world. At the close of the war the Zschopau works was seized and dismantled by Soviet forces, eventually becoming the site of MZ motorcycle production. After merging in 1947 with Auto Union DKW Germany was re-admitted into the FIM in 1951 which by then had banned supercharging in motorcycle racing. DKW / Auto Union renewed its racing program with naturally-aspirated two-strokes, only to cease their racing activities forever after the 1956 season.
During the Classic GP Assen the 1939 DKW SS 350 LADEPUMPE is ridden by German Eberhard Uhlmann in the Motorcycle Legends GP1-category.