Let’s get right to the point. There’s a certain style and feel we try hard to maintain at 95 Customs. Our attention is focused on items from a different time, and on people, places, and things with sporting intentions. So it stands to reason that, while we motorcyclists need to stick together and embrace riders with different proclivities than we may have, we are not a Harley Davidson site, per se. Except for the 1972 XRTT 750.
It all started wen 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 the high-level riders from the States competing on dirt ovals. The dirt ovals are, oddly enough, where the XRTT got it’s 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 light weight nimble look of the Triumphs of the time.
But for all the weight savings, the newfound power, and the elegant body, the failure of the design was the clunky four speed gearbox. It may have been a cartridge style set up, but it was, for all intents and purposes, carried over from the legacy design.
Perhaps one of the smartest things Harley Davidson did in preparation for the Trans-Atlantic Match Race Series was to bring Cal Rayborn with them. He was a factory Harley Davidson rider who had won the 1968 and 1969 Daytona 200 races, in addition to setting two motorcycle land speed records in 1970.
In reality, the XRTT was a pretty primitive motorcycle, and was probably comparable at best with the other bikes in the field, but Rayburn skillfully muscled the XRTT through the pack in various races, winning three of the six races in the series, and tying for the championship in final season points.
Not long after the success of the XRTT, the multicylinder four stroke and two stroke motorcycles from Japan moved into the larger displacement road racing classes. They quickly began to dominate, making the XRTT irrelevant almost immediately after its success.
It is rumored that Harley Davidson built between 18 and 23 examples of the XRTT750. Most of them are either in museums or safely stored in private collections. But there are a couple that are brought out to events like the Goodwood Festival of Speed to share with the world.