Originally posted on Riding Vintage.
In the 1930′s, speedway racing was rising in popularity across the US. British JAP and Rudge machines dominated the sport, racing on tracks covered with fine cinders (a by product of coal fired plants). This was more than Harley-Davidson factory racer Joe Petrali could take and he urged Harley to build their own speedway racer. It is rumored that Harley was not interested in the project at all, but let Petrali build the motorcycle himself at the HD plant on the weekends. Whether it was Petrali or a team of HD engineers, a new machine designated CAC was released in 1934.
The CAC was powered by a 500cc single-cylinder engine which borrowed heavily from the British JAP engine. The compression ratio was a whopping 16.5:1 and the engine revved up to 6,000 rpm. There was no transmission or clutch as the engine was directly connected to the rear wheel by a short-coupled jackshaft and drivechain. Brakes were left off too, because racing is about going fast, not stopping.
There seems to be some question as to the number of CAC actually built. Harley-Davidson states that they built 20 complete race bikes and 5 spare engines. Many other sources claim that only 12 complete machines were built. Either way, it is an extremely rare machine with only nine machines currently known to exist.
If you read Harley’s press release for the CAC, it sounds like quite a machine: “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.” Not the kind of machine you would expect to be cancelled after one year of production, but that’s exactly what happened. More rumors abound about why Harley ceased production; cam issues, cam timing problems, poor performance etc.
Still, I’d like to see one sliding around a corner on a cinder track…