[2][3][4][5] The XR-750 is associated with the careers of racers Mark Brelsford, Cal Rayborn, and Jay Springsteen, and was the favorite motorcycle of stunt performer Evel Knievel.

[8] Over time, this displacement advantage kept the older flathead technology on the track and discouraged a broader field of competitors.

[8] The flathead Harley-Davidson KR series had dominated Class C racing, but by the late 1960s BSA, Norton and Triumph had little market for 500 cc OHV motorcycles, and there was increasing pressure for a single displacement, without reference to valve configuration.

[8] The public was buying 650 cc (40 cu in) and larger displacement British bikes, and they would prove to be competitive, given the chance.

OHV engines began to dominate racing, in spite of Mert Lawwill's efforts to delay the inevitable on his flathead Harleys, and the KR bikes were a decade out of date and could no longer compete successfully.

[8] With limited time and money in 1969, Harley-Davidson's racing manager Dick O'Brien and his team used elements of existing designs to put together a new OHV racer, but rather than start from scratch they decided to modify their existing OHV racer: the Sportster-based 900 cc (55 cu in) XLR magneto-equipped race engine with a 3.0000 in (7.620 cm) bore and a 3.8125 in (9.684 cm) stroke.

The frame and the running gear were held over from the KRTT racer, with a Ceriani front fork and two Girling rear shocks.

[8] The fuel tank, fenders, and rear seat/fender combination were fiberglass, with a snap down seat cover over a foam cushion.

[8][9] To comply with AMA homologation rules, two hundred examples were made and could be had upon request at Harley-Davidson dealers, at a price of US$3,200, which today with inflation would be about US$ 25,106.

[9] Like the dirt tracker, it used a Ceriani fork and Girling shocks, two 36 mm Mikuni carburetors and tuned dual reverse cone exhaust.

Adapted with mechanical fuel injection and nitrous oxide, Gerencer estimated his engine produced over 150 hp (110 kW).