WITH the air-cooled, push-rod overhead valve XR750 now in its 44th year, there is plenty of speculation that Harley-Davidson will replace it with a racing version of its new 750cc water-cooled 60 degree V-twin.
Harley-Davidson has enjoyed incredible success with the XR750, but when it made its début back in 1970, no one would have predicted it would still be winning races in 2014. In fact in the first two years with the new overhead valve racer, Harley-Davidson’s race chief Dick O’Brien struggled to make it competitive with the English 750cc OHV parallel twins from BSA, Triumph and Norton. Those first XR750s struggled to match the power output of the side valve KR750s they had replaced.
Then O’Brien and his team made a break-through in port design and started to challenge the competition, well on dirt-tracks at least. In road racing, the XR750TT was struggling against Yamaha’s air-cooled 350cc TD-3 and pretty much outclassed by the water-cooled TZ350 that followed, let alone the three cylinder two-strokes from Kawasaki and Suzuki. If that wasn’t bad enough, along came the four cylinder TZ700 and it was game over.
However, Harley’s fortune’s in dirt-track racing went in the opposite direction to the road-racers. As the road-racing XR750TT struggled, the dirt-track XR750 got rolling. Mark Brelsford was the first man to win the AMA Grand National Championship on the XR750. That was in 1972.
But then Yamaha got Kenny Roberts onto a bored out XS750 dirt-tracker, and armed him with a TZ700 road-racer. Kenny then went on to win back-to-back Grand National Championships in 1973 and 1974 before Harley-Davidson took over. Later on the American Motorcyclist Association separated the road-racing series from the Grand National Championship so Harley had an even stronger grasp in that arena.
|Kenny Roberts in action on the 750cc OHC Yamaha XS650 in 1975.|
Rex Beauchamp on a factory XR750, one of many
to win on the push-rod Harley.
However, with the series an all-Harley show, the AMA bowed to lobbying from Honda and allowed the limited edition overhead cam four-valve RS750 into the series. Honda then went on a winning streak, taking the Grand National titles in 1984 (Ricky Graham), 1985, 1986 and 1987 (Bubba Shobert).
At this point the best RS750s were making around 125 bhp while the two-valve XR750s were making around 119 bhp. This was staggering performance and it exacted its toll. The Harley required frequent rebuilds and both brands ended some of the mile races on the cords of their rear tyres.
Scott Parker won a record nine AMA Grand National
Championships on the XR750, and racked up
55 wins in mile races and 35 on half-miles.
The AMA was deeply concerned about this and introduced across the board 33mm intake restrictors. This brought the Honda and the Harley down to 112-115 bhp. With parity between the brands, Harley started winning again. And it has kept on winning. But there’s a new challenger in the form of the DOHC, 8-valve liquid-cooled Kawasaki 650 parallel twin.
|The Howerton Motorsports framed Kawasaki that |
Bryan Smith raced in 2012 and 2013.
However, the Kawasaki struggled on half-miles and also had trouble getting traction off the corners on many of the other mile tracks, so Harley-Davidsons did most of the winning.
That has continued to this year. Now riding for the Villa Esparza/Crosley Radio Team, Smith has Jeff Gordon-tuned, Kawasaki 750cc engines and many other components from the 2012 and 2013 Howerton Motorsports machine, in a highly modified C&J chassis by Robert Terando.
It has proved a winning combination and in July the team made another milestone, winning the Hagerstown half-mile. This was the first time the Kawasaki had been able to beat the Harleys on a half mile. And with wins on the mile tracks of Springfield, Sacramento and Colonial Downs, plus podium scoring rides elsewhere, Smith leads the GNC by nine points over Harley privateer Jared Mees with just two rounds remaining.
|Bryan Smith has the Villa Esparza/Crosley Radio Team Kawasaki out in front of the Grand National Championship with just two rounds remaining. Will he be the first |
man to take the title on a Kawasaki?
If Smith carries his points lead through the next two races, he will snatch the AMA Grand National Championship from Harley-Davidson’s grasp for the first time in 27 years.
That is not something Harley-Davidson’s stronger dealerships are going to take laying down. So you can bet they have been beating on the factory door pleading for an XR750 replacement.
|The 750 Street uses an all-new engine. Will Harley-Davidson |
use this as a basis for a new dirt-track challenger?
At the recent US dealer convention, Harley wheeled out a new water-cooled racer powered by the water-cooled OHC, 8-valve 750cc Revolution X engine from the new 750 Street.
Whether this is a factory deal or a Vance and Hines limited edition dirt-tracker remains to be seen. Critics of the current MBA-dominated Harley management say they have seen precious little evidence that the current executives know anything about the company’s history, especially when it comes to dirt-track racing.
Perhaps they are about to be proved wrong!