To power his custom motorcycle, the Flying Millyard, craftsman Allen Millyard constructed this monster V-twin from two cylinders of a World War II-vintage aircraft engine. How does it run? Awesome. Watch this. 

If the cylinders on the engine pictured here look familiar to you, you know your aviation history. The exquisitely finned components are from a Pratt & Whitney R-1340 Wasp, a 9-cylinder, air-cooled radial aircraft engine that saw duty from the ’20s through World War II. Motorcycle builder extraordinaire Allen Millyard (check out his amazing YouTube channel) used the P&W Wasp bits to construct a monster V-twin to power his vintage-flavored custom motorcycle, the Flying Millyard.

Previous Millyard creations include a Viper V10-powered road bike and a lovely 1600cc Kawasaki V8 motorcycle based on Z1 components. This beast, employing a pair of Pratt & Whitney cylinders and heads, features a perfectly square bore and stroke of 5.75 inches for a total displacement of 4893cc, or 299 cubic inches. (The original 9-cylinder radial version displaced 1340 cubic inches, hence the U.S. government designation R-1340.) For a V-twin, the Millyard presents an interesting exercise in scale, weighing a reported 250 lbs. bare. And when it starts and runs, the engine projects authority, to say the least. Turn up the sound and check out the video below.