It all started when the folks at BSA, in an attempt to drum up some publicity, initiated a race series in the UK called the Trans-Atlantic Match Race Series. It consisted of six races that pit British and American bikes against one another on road courses. The conventional wisdom was that the Americans would be hilariously outmatched, since most of the high-level riders from the States competing on dirt ovals. The dirt ovals are, oddly enough, where the XRTT got its start. The Harley Davidson XR bikes and engines, developed to replace the KR engine, were first used on the dirt ovals. The early versions of the XR engine utilized cast iron head and cylinder sleeves. In addition to being heavy, they produced less power than the KR they replaced. They also earned the moniker of ‘waffle iron’ because they would get so hot they’d burn the rider with even the slightest contact. Mert Lawill once described the early XRs as,”Agony. That’s the XR. That thing took 10 years off my life”.

​

Dramatic changes were made to the XR for 1972. The new plant used the same basic pushrod 45 degree V with 2 valves per cylinder architecture but received aluminum alloy heads and sleeves, and a pair of new 36 mm Mikuni carburetors. The new engine also did something few air-cooled Harley engines ever do - it revved to 8200 RPM, and even had revs to spare. That's essentially 2000 RPM higher than the equivalent engine in their street bikes. This redesigned engine immediately generated 73 hp out of the box- 9 more horsepower than the previous iron version. With some massaging, they could produce as much as 90 hp. The new XR alloy engine went on to dominate the dirt ovals. It is that engine that was the foundation of the XRTT. 

They started by wrapping a chromoly chassis around the new engine, and gave it a diminutive 54 inch wheelbase and a steering rake of only 24 degrees. Those dimensions gave a level of nimbleness and agility otherwise never associated with Harley Davidson. They also knew that weight would be key. It became a bit of an obsession for the XRTT development team. The bike wasn’t equipped with any gauges beyond a tachometer. Nor was it given a kickstart lever. It could only be pushed or started on rollers. It had clip-ons versus handle bars - all in the interest of saving weight. And it worked. The XRTT weighed in at a mere 320 pounds. 

​

The bodywork is very elegant, particularly considering it came from a company who practically never develops full coverage racing bodywork. Compared to the British bikes it ran against, the XRTT looked large. The tall gas tank and high seat hump gave the Harley a big, muscular look, relative to the lightweight nimble look of the Triumphs of the time.

​