In the mid-1970s, Harley-Davidson, then owned by AMF, started planning for the future. They needed to replace the long-in-the-tooth Ironhead and Shovelhead engines, but they also started another, more ambitious project—a modular, liquid-cooled family of engines that would power a whole new line of motorcycles. Harley-Davidson enlisted the help of Porsche in the design of this modular engine, and they came up with a V-twin of 400-500cc that could be doubled into an 800-1000cc V-4, and even tripled to a 1500cc V-6.
Back to the Future
The first concept bike was the Nova, a V-4-powered tourer that bristled with innovation. The engine was a stressed member, so there were no down tube frames. The radiator was tucked under the seat (fed by air ducts on the tank) to keep the view of the engine clean. The fuel tank was actually an air box, and the real fuel tank was beneath the seat.