This 1972 XRTT road racer model is powered by the improved steel-sleeved aluminum alloy version of the XR racing engine, which debuted the same year.

The 1970 XRTT-750 road racer features a full fairing and an oversized 6-gallon fiberglass fuel tank, a necessity for long races such as the grueling Daytona 200.

An employee assembles one of two hundred new XR-750 models built for the 1970 season.

Legendary Harley-Davidson racer Cal Rayborn crosses the finish line at the 110-mile-long road race at Indianapolis Raceway Park, 1967.

Designed to celebrate the 1969 Grand National Championship title won by H-D team racer Mert Lawwill, the famed “#1” logo made its first appearance on this poster.

The April 1968 cover of the Harley-Davidson Enthusiast commemorated Cal Rayborn’s run at Daytona, the first of his two back-to-back victories on that track. In 1968, he became the first competitor to average over 100 mph during the 200-mile race.

Race team director Dick O’Brien takes a closer look at a race bike in 1978. Over the course of his decades-long career with H-D, he led factory riders to 16 AMA Grand National Championships, and oversaw the development of the highly-successful XR-750 racing motorcycle.

The H-D factory crew works on Cal Rayborn’s XR road racer.