Summary

• The XR750 was Harley-Davidson’s most profitable bike constructed for the race observe.
• It has gained 28 of the 37 AMA Grand National Championships from 1972 to 2008.
• This was the bike of alternative of legendary American stuntman Evel Knievel for his many death-defying jumps and stunts.

If you possibly can rely the variety of iconic bikes Harley-Davidson has produced within the final 120+ years, you would want extra fingers and toes. One specific mannequin that thrived on pure adrenaline on racetracks is the legendary XR750. With a wealthy historical past within the dust and dust, it was born in 1970 as an engineering marvel to exchange the outgoing KR750 because the new-and-improved race-ready observe bike.

For over 50 years, the naturally athletic XR750 would show itself time and time once more as a pressure to be reckoned with. Powered by a Sportster-based engine, this bike utilized cast-iron heads and cylinders, a magneto as a substitute of a generator, and improved oiling. By 1972, a extra highly effective all-aluminum alloy engine was launched to the XR750. With a extra highly effective drivetrain and nimble nature, this bike would dominate racetracks up till 2008, successful 28 out of 37 AMA Grand National Championships. This earned it the title of “the winningest motorcycle in AMA Pro Racing motorcycle history.” Today, we glance again at its glory days.

The following article was primarily based on the XR750’s historical past as a part of the Harley-Davidson lineup, and general driving expertise sourced from OldBikeBarn.com , ClassicMotorcycleBuild.com , National Mecum Museum , and Harley-Davidson .

Brits Inspired AMA To Build Bikes Up To 750cc

Leading as much as the event of the XR750, British producers and racers influenced the AMA to function bikes with engines as much as 750cc during which each facet and overhead valves might participate within the races. In response, the racing and engineering minds at Harley-Davidson felt compelled to give you a brand new bike that may very well be a critical contender on the observe towards the English. Harley-Davidson Race Team Manager Dick O’Brian and his staff helped design the XR750 that may not solely go on to exchange the KR750, however would additionally proceed to be one of many highest-performing motorcycles in the world of competitive racing.

The 45 Degree V-Twin Aluminum OHV Engine Was The Beating Heart of the XR750

At the time of its inception, Harley-Davidson’s line of XLRs came equipped with 900cc V-twin engines. In order to satisfy race spec calls for to have the XR750 qualify, Harley’s racing staff wanted to discover a approach to tone down the Sportster engine’s energy output, and nonetheless be the highest-performing bike on the observe. After some tinkering with the bore and stroke, engineers have been efficiently capable of dial it again to 750cc.

For a motorbike meant to be highly effective, gentle, and nimble on the observe, Harley-Davidson made the clever resolution of growing the XR750’s 45 Degree Aluminum V-Twin engine primarily based on its pre-existing Sportster engine. In 1972, Harley improved upon the XR750 by changing the forged iron heads with aluminum alloy to be lighter and extra heat-resistant, in addition to some tinkering with the bores and stroke to pack in a number of extra horses.

1972 Harley-Davidson XR750 Engine Specs

The XR750 Needed Work Done Before It Could Race

Make no mistake. Just as a result of the XR750 has gone down in historical past as a profitable bike in AMA Pro Racing does not imply it occurred in a single day. Like any professional athlete, the Harley-Davidson racing staff wanted to do quite a lot of analysis, trial, and error earlier than they have been capable of engineer the XR750 into racing perfection. The authentic mannequin utilized cast-iron heads, which proved to be problematic as a result of their tendency to overheat except ridden in cooler climate. In addition, ought to the metallic calm down too rapidly, the heads might probably crack. While the unique XR750 faired effectively briefly races and funky climates, something hotter or longer would danger malfunctioning.

By 1972, Harley-Davidson improved upon the XR750’s overheating drawback by changing the cast-iron heads with aluminum. This metallic proved itself to be each lighter and extra heat-resistant, permitting riders to push the bike more durable throughout longer races with out inflicting additional injury. The engine was additionally positioned as distant from the carburetor as attainable to assist with the bike’s cool-down. By stopping the bike from heating up as rapidly because it used to, the XR750 was capable of keep at a extra secure temperature for longer intervals.

Engineers additionally wanted the bike to slim down, too. In addition to the aluminum heads, Harley engineers launched aluminum spoked wheel rims, a 2.5-gallon fiberglass gasoline tank, and a light-weight fiberglass seat. With these modifications, the XR750 utterly annihilated the competitors. Today, Harley-Davidson continues to be an energetic contender on the racetrack. But somewhat than the XR750, the race staff swimming pools their vitality, time, and sources into their model of a high-performance Road Glide for the popular King of the Baggers race series.

The XR750 Was Popularized by Evel Knievel

Having a popularity for being one of the unbeatable bikes on the racetrack was already an enormous enhance for the XR750. But when it grew to become the bike of alternative for legendary stuntman Evel Knievel, that’s when its recognition actually and figuratively took off. He properly went with the newer model of the XR750 as a result of it being lighter than the unique (a extra aerodynamic choice when performing his death-defying stunts).

As quickly as avid followers noticed the bike that Knievel was utilizing to leap every little thing from a number of automobiles, Greyhound buses, and Mac vehicles, everybody needed to be like him. So what higher manner than to get their palms on the identical bike that he was driving? Whether they have been capable of stick the landings in addition to him relied on who was making an attempt the jumps, although.

1972 Harley-Davidson XR750 Specs

50 Years of Excellence

With over 5 a long time of victories below its belt, the Harley-Davidson XR750 secured itself a spot in bike historical past as one of the legendary bikes to ever hit the observe and the streets. After all, a light-weight weight, with a robust race engine constructed to spec, and a refined cooling system, the XR750 had perfected a recipe for fulfillment that proved itself time and again as a critical contender.

While it was an enormous cultural sensation within the U.S., its legend prolonged to different avid followers internationally as effectively. Though its manufacturing was finally discontinued in 2013, the XR750 achieved such an iconic standing within the motorcycling world that it stays a success within the used market.

Today’s Successors

Harley-Davidson’s XR750 by itself might be argued to be in a category completely of its personal. One half Sportster, one half race bike, and one half off-roader. It was the right end result of a number of parts that made it one of many producer’s most profitable fashions in its 120+ yr historical past. Even after 50 years of manufacturing, this bike nonetheless carries a wealthy historical past of excellence. Though now not in manufacturing, components of the XR750’s DNA might be seen in a few of immediately’s newer fashions.

Following in its dirt-ridden tire tracks is Harley’s first ADV mannequin, the Pan America. Able to dominate the streets in addition to robust terrain, this bike dons the mighty Revolution Max 1250 engine that has sufficient horsepower and torque to achieve 60mph in 3.4 seconds. The identical might be mentioned for Harley’s revamped line of Sportsters. The Sportster S follows the XR750’s flat observe components, all whereas being as gentle as attainable. This makes them the lightest variations of the Sportster class in Harley-Davidson historical past.

Harley-Davidson XR750 Key Features

• 750cc air-cooled V-Twin engine
• 4-speed transmission
• Won 28 of 37 AMA Grand National Championships
• Lightweight, heat-resistant aluminum heads
• Chain drive