1934 Harley-Davidson CAC Racer: Factory Speedway Bike, History & Specs

The 1934 Harley-Davidson CAC was the company’s short-lived factory speedway racer, built to compete with dominant British machines on American cinder tracks. This article covers the CAC’s origins, engine design, production numbers, and why Harley-Davidson abandoned the model after just one year.

For more early Harley-Davidson racing and factory history, see the History section.

In the 1930s, speedway racing was growing quickly across the United States. British JAP and Rudge machines dominated the sport, racing on tracks covered with fine cinders, a byproduct of coal-fired plants. Harley-Davidson factory racer Joe Petrali had seen enough of that and pushed Harley to build a speedway racer of its own. It is rumored that Harley had little interest in the project and simply let Petrali work on it at the factory on weekends. Whether the project was driven by Petrali or a group of Harley engineers, the new CAC appeared in 1934.

The CAC was powered by a 500cc single-cylinder engine that borrowed heavily from the British JAP design. Compression was a whopping 16.5:1, and the engine revved to 6,000 rpm. There was no transmission or clutch, since the engine was directly connected to the rear wheel by a short-coupled jackshaft and drive chain. Brakes were left off too, because speedway racing is about going fast, not stopping.

There is some disagreement over how many CAC racers were actually built. Harley-Davidson stated that it produced 20 complete race bikes and 5 spare engines, while many other sources claim that only 12 complete machines were built. Either way, it is an extremely rare machine, with only nine currently known to survive.

Harley’s own press release made the CAC sound like a serious contender: “The short track racers we are offering are the result of much study and actual trial by our racing department. Extensive tests were conducted on the West Coast on actual tracks with outstanding short track racing stars and in competition with the best of the foreign machines. Our experimental machines came through every test with flying colors. Improvements incorporated as a result of these trials will make these new racing models even better in power and performance.”  It doesn’t sound like the kind of machine you would expect to disappear after one year, but that is exactly what happened. Rumors about the cancellation include cam issues, timing problems, and disappointing performance.

Still, I’d like to see one sliding sideways through a corner on a cinder track...

For more early Harley-Davidson racers and competition history, see the History section.