This Righter 4034 engine, one of nine total built, was intended to power radiocontrolled gunnery target drones and postwar, selflaunching sailplanes. It is a four cylinder, twocycle, simultaneouslyfiring (in opposing cylinder pairs) engine of 34 cubic inch displacement (554 cc) that made 17 horsepower at 3,800 rpm. Ignition was of the batterypointsdual coil type. The 4034A with topmounted, unthrottled carburetor was test flown in 1944 in the oneoff, experimental Radioplane RP9 aerial gunnery target drone which achieved 133 mph in flight. The 4034A, with a lowmounted, throttled carburetor and pullstarter, was also used in the postwar, 1946 NelsonBowlus Bumble Bee, a twoplace, retractable landing gear, selflaunching sailplane. Video of the Bumble Bee can be found here:    • F 3520 The Nelson Bumble Bee/Dragonfl...  
At only 17 horsepower, the Righter 4034 provided minimal flight performance in the Bumble Bee and was replaced with Nelsonbuilt engines of 25 and 28 horsepower in the followon, limitedproduction Nelson Dragonfly aircraft. There are six known surviving Righter 4034 engines, however as of July 2022, this is the only running example. Based on the geometry of the nose thrust bearing retainer, the rear case machined from aluminum billet, and the absence of a data plate or any evidence that a data plate was ever attached, this engine may have been an early experimental or development model. The internal condition of the engine indicates it had been refurbished before being sold as government surplus in 1945.