Harley-Davidson XR-750 — Wikipedia, the free encyclopedia

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Harley-Davidson XR 1200 Concept

Harley-Davidson XR-750

An XR-750, 16, through the dust at Scioto Ohio

The Harley-Davidson XR-750 is a motorcycle made by Harley-Davidson 1970, primarily for dirt racing. but also for road in the XRTT variant. The XR-750 was in response to a 1969 change in AMA National Championship rules leveled the playing field for other than Harley-Davidson, Japanese and British motorcycles to the previously dominant Harley-Davidson KR bike. [ 1 ] The XR-750 went on to the winningest race bike in the of American Motorcyclist Association racing. [ 2 ] [ 3 ] [ 4 ] [ 5 ]

The XR-750 is associated the careers of racers Mark Cal Rayborn. and Jay Springsteen. and was the favorite of stunt performer Evel [ 6 ] Knievel used the bike December 1970 until his jump in January 1977. An was included in the 1998 The Art of the Motorcycle and one of Knievel’s bikes is in the Smithsonian’s Museum of American History on the Move exhibit. [ 1 ] [ 7 ]

Rule changes obsolete KR [ edit ]

2.75USqt (2,600ml)

The AMA National Championship Class C introduced in 1933 and revised in had an equivalency formula limiting or sidevalve, engines to 750cc displacement. while more overhead valve (OHV) could be a maximum of only (31cuin). [ 8 ] Over time, displacement advantage kept the flathead technology on the track and a broader field of competitors. At 200 homologated examples of a model had to be and made available to the public. [ 8 ] The Harley-Davidson KR series had dominated C racing, but by the late 1960s Norton and Triumph had little for 500cc OHV motorcycles, and there was pressure for a single displacement, reference to valve configuration. [ 8 ] The was buying 650cc (40cuin) and displacement British bikes, and would prove to be competitive, the chance. [

8 ]

Harley-Davidson XR 1200 Concept

With the British marques influence in the AMA, in 1969 new were established that would be one maximum displacement for track racing, 750cc, no regard for valve type, the 500/750 OHV/sidevalve split was for the time being in road OHV engines began to dominate in spite of Mert Lawwill efforts to delay the inevitable on his Harleys, and the KR bikes were a out of date and could no longer [ 8 ]

Development [ edit ]

With time and money in 1969, racing manager Dick and his team used elements of designs to put together a new OHV racer. [ 8 ] The cylinder. aluminum head (45.6cuin) V-twin four-speed of 1970 was based on the mass Sportster XL dating to 1952, but modified heads and cylinders, a instead of generator, and improved [ 8 ] The frame and the running gear held over from the racer, with a Ceriani fork and two Girling rear [ 8 ] The fuel tank, fenders, and seat/fender combination were with a snap down cover over a foam [ 8 ] [ 9 ] To comply with AMA homologation two hundred examples were and could

be had upon request at Harley-Davidson at a price of US$ 3,200, which with inflation would be US$ 19,433. [ 9 ]

Not unlike other Harley-Davidson the unit construction left and engine cases split and formed four cavities: a front crankcase, a center gearbox. a right side gearcase for the timing train, the four camshafts are housed, and a cavity for the three row primary chain. [ 8 ] A row of four camshafts had been used on the KR racers, from the sidevalve Model WL. and earlier Model D of 1929. [ 10 ] the single camshaft of other designs was cheaper to manufacture, and four cams allowed performance, such as greater in adjusting the cam timing, and the short camshafts are durable, and give the a straigher path to the rocker [ 11 ]

XRTT road racer [ ]

Harley-Davidson XR 1200 Concept
Harley-Davidson XR 1200 Concept
Harley-Davidson XR 1200 Concept
Harley-Davidson XR 1200 Concept

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