Sankyo also produced a new engine in 1947, based on the 1935 750cc flathead engine which Harley-Davidson used in the RL. This was not an exact copy as the Shinagawa factory no longer had access to blueprints from Harley-Davidson. It was most likely reversed engineered by the Japanese. They also improved the transmission by adding a reverse gear for use on sidecar models.
The Rikuo remained popular during the postwar era and was the official vehicle of the Japanese police force. Production rose to roughly 2000 motorcycles per year and additional improvements were made, including a telescopic front fork and aluminum heads. The new Rikuos were styled after the current models from Milwaukee, with the exception of the engine, which remained the 750cc flathead.
The Shinagawa factory was bought in 1950 by the Showa Aircraft who was also building clones of BMW and BSA motorcycles. Production continued until 1959 when Rikuo finally went out of business, although an unknown number of motorcycles were assembled from spare parts until 1960.
