The Kemp Machine Works of Muncie, Indiana built several types of air-cooled engines for airplanes, motorcycles, ice boats, and air-drives for boats. Due to its simple design and quantity production, this engine sold for approximately one half the price of its water-cooled competitors, and was lighter, more streamlined, and trouble-free than most of them.
Early models such as this one had concentric valves, which presented a large valve area, but a complicated design. Later models were equipped with conventional valves. All of the 2-, 4-, and 6-cylinder models had automatic intake valves.
A Kemp Model D-4 powered Walter Ralston's 1912 biplane.
This object is not on display at the National Air and Space Museum. It is either on loan or in storage.