Evel Knievel on the Harley-Davidson XR 750
HARLEY-DAVIDSON CELEBRATES THE 50TH ANNIVERSARY OF THE XR-750 Flat Track

Quick and dirty

Harley-Davidson is celebrating the 50th anniversary of the XR-750

  • The most successful racing machine of all time
  • Stunt bike for Evel Knievel and exhibit in the Guggenheim Museum
  • The engine of the successor is based on the engine of the XG 750 Street

(Neu-Isenburg, June 3rd, 2020) She is a child of the late sixties and the XR-750 owes its birth in 1970 to the fact that the American motorcycle racing association AMA (American Motorcyclist Association) had changed the regulations in flat track. The new guidelines no longer gave side-controlled engines, which Harley-Davidson had successfully used in its KR racers, a chance.

Harley Davidson XR 750 21
Harley Davidson XR 750 21

A 750cc OHV engine was needed - and Harley's racing manager Dick O'Brien and his team built it based on the V-twin that was used in the Sportster racing machine XLR. In the new Flat Tracker, the tuned engine was housed in a modified KR racing frame, which was refined with Ceriani forks and Girling shock absorbers and crowned by a fiberglass tank and tail in Harley's racing color Jet Fire Orange. Racing tires were put on the lightweight 4×19-inch spoke wheels and the 2.8 liters of engine oil circulated through an optimized circuit.

Harley Davidson XR 750 21
Harley Davidson XR 750 21

The machine weighed just 134 kilos and she was a truly fiery lady: a quarter turn of the throttle was enough to fully open her throttle. 200 units were produced to comply with AMA regulations. A racing driver had to pay 3,200 US dollars for a copy - not including brakes, because in the flat track you only need one of them and the teams could retrofit them at the rear according to their personal preference.

Two years later, the The engineers turned the rear cylinder around so that there was space for two 36 carburetors with massive air filters on the right and a raised exhaust on the left. The crankshaft, connecting rods, pistons and valves were redesigned with a modified bore-stroke ratio.

Harley Davidson XR 750
Harley Davidson XR 750

More power and unadulterated stability were the reward for the effort and now other teams were able to get involved as the XR-750 was preparing to dominate the flat track. Between 1972 and 2008, it won 29 of the 37 AMA Grand National Championships - constantly being optimized - and it has more racing victories to its credit than any other motorcycle in the history of the AMA, giving it the title of “Most Successful Racing Machine.” of all time”.

Stuntman Evel Knievel performed his most spectacular jumps on it and the Guggenheim Museum chose it as one of the jewels in the exhibition The Art of the Motorcycle. Their street-legal derivatives include the XR 1000, introduced in 1983, and the XR 1200, which was launched in 2008.

Harley Davidson XR 1200
Harley Davidson XR 1200

Since the beginning of the 1980s, Harley-Davidson only manufactured engines instead of complete XR-750 race bikes and ensured the supply of parts for the racing teams, who were now happy to put their chassis together on their own anyway. At the end of the eighties there were only parts instead of engines. Anyone who owns one of the just over 500 complete bikes from Milwaukee can consider themselves lucky, because it is now worth many times its original price.

Even today, XR-750 racing machines - now with over 100 hp - thunder over American flat track slopes, but Harley-Davidson now has a crown princess of the classic sports canon at the start: the XG 750R, whose liquid-cooled 60-degree V2 Based on the Revolution-X engine of the street models, it is about to follow in the footsteps of its great predecessor - a fascinating piece of technology, but unfortunately "for race use only"!

If you want to get to know the roadworthy and registrable Harleys, stop by your nearest authorized dealer. You can find it at www.Harley-Davidson.com .

 

Text and image credits: Copyright Harley-Davidson


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