XTreme XRs

XTreme XR's: A Milestone Motorcycle Still Chewing up the Miles


Milwaukee's Racebred XR 

You could have any color you wanted as long as it was Jet Fire Orange.

For some 34 years running, the XR750 has been the ultimate "do it in the dirt" warrior, its victories literally spanning decades and dirt (and paved) tracks across the country, both in the hands of factory-sponsored pro's and independent riders as well. Introduced in 1970, the XR750 took over where the vaunted KR-TT's left off. Its first couple years, run with iron barrels, were problematic, but when fitted with aluminum cylinders and cylinder heads the new factory racers found their stride. Equipped with Ceriani forks and Girling racing shocks, the engines were stuffed into welded, tubular 4139 steel frames, its aluminum spoked wheels shod with Goodyear rubber. While the early ironhead design, basically a destroked 880cc Sportster, made for 70 hp, the aluminum upgrades, combined with polished valves, pistons and cams, chromed valve stems, and compression bumped from 8:1 to 10.5:1 brought out 20 more ponies, the XR's cranking out 90 hp in a bike that tipped the scales at 290 lb. Dual 36mm Mikuni's fed the hypo-ed Sporty motor, a 4-speed tranny shifted through a dry clutch and spark was provided by a Fairbanks-Morse magneto. You could have any color you wanted as long as it was Jet Fire Orange. Its lightweight precluded a starter of any kind, so it's a hump and bump roll-on to get it fired up. Here's the x-iest of the XRs... first off the H-D hand assembly line.

Once fired up, you'd better get a grip. Think of a stump-pulling torquey, pit bull tough, light as a butterfly/sting like a million bees bike and you've got the gut feeling of riding an XR. Only one-quarter turn on the throttle goes from nada to WFO and it pulls without letup from 2000 rpm on up the scale and off it. While there's a rear disk brake, riders usually relied on engine compression to bring the bike down to non-warp speeds.

It should be noted the initial design for the XR750 is credited to a Dutchman by the name of Pieter Zylstra, and the first factory bikes tended to overheat, earning the less than favorable moniker as the "Waffle Iron." It was the legendary Cal Rayborn who brought the XR its first fame. Riding a Walt Faulk prepped bike, he won three out of the six British-American "Transatlantic" races. Think of a stump-pulling torquey, pit bull tough, light as a butterfly/sting like a million bees bike and you've got the gut feeling of riding an XR.Not content with mere roadracing, Cal piloted an XLR-engined streamliner to a land speed record of 265 mph at Bonneville. Sadly, Cal died in a 1974 crash aboard a Suzuki at age 33. Later Team Obsolete would campaign Cal's XR750.

Mert Lawwill rode more than one XR750. His 1974 Harley-Davidson XR750, owned by Carl Fronk of Langhorne, Pennsylvania, resides in the Motorcycle Hall of Fame Museum at AMA headquarters in Pickerington, Ohio. This XR750 featured Axtell heads, Lawwill's own special-grind cams and his chassis design. The same bike would be later campaigned by Mike Kidd, a member of the Kenny Roberts/Mert Lawwill racing team that was fielding a Yamaha dirt-tracker. Often aboard the venerable XR, Kidd edged out Gary Scott by just 5 points--200 to 195--to take the Grand National Championship. In other words, a bike that won the National Championship twice for its riders. Both Lawwill and Kidd were inducted in the AMA Hall of Fame and the bike is there for all to see.

XR1000 1983-4: A Factory Built Streetable XR

Some dealers were even giving free gas if you bought an 'XR1000. IN 1983 the Factory unleashed the XR750-inspired XR1000, a street bike you could find at your local H-D dealership. You could run it on the street or compete in the AMA Battle of the Twins road race series. When first introduced, some 20 years ago, it carried a price tag of $6800. What you got was 70.6 hp at 5600 rpm while a stock XL produced 56. You could also bolt on factory race kit parts and up the ante to 90 hp which put you up with the factory XR750. While compression ratio was down one knotch to 9:1, the XR1000 benefited from Branch Flowmetrics heads and dual Del'Orto slide carburetors. The frame came over from the Sportster XL models, and weight was 480 lb, almost 200 more than the XR750, but it featured disk brakes front and aft. Designed, built and made ready for the AMA series in just 60 days, the Milwaukee wunderkind was the work of H-D Racing Director Dick O'Brien. On its first foray the XR1000, in the hands of Jay Springsteen, won the first Battle of the Twins in Daytona in March 1983. (If you're wondering how old Jay is, he joined the factory team in 1976 at the ripe age of 19 and promptly won the Grand National Championship during his first year at bat. And he's been swinging ever since.)

When riders first saw the XR1000 at the dealers, the level of enthusiasm was not as high as hoped for by the Motor Co. Some people whined about getting their legs around the protruding carbs and huge air filters. Others thought they were too expensive. Some said with only a 2.5 gallon gas tank how far could you get with a thirsty bike. The XR1000 was in production only for two years, 1983 and 1984. All the naysayers aside, today the XR1000 is now up on the pedestal as a collector piece. 

No problem. I got the hang of it after the first two or three hundred times. Blurring the distinction between street and track bike.

Mike Bowen's Pitbull Streetster: An XR with Teeth

If you saw "Kill Bill" you've seen Mike Bowen in action on the silver screen. He played "Buck" the lecherous hospital attendant "servicing" the injured Uma Thurman and ends up with his head used as a doorstopper. The half-brother of actors Richard and Keith Carradine, Mike's been in something like 50 films including Godfather III and on TV shows like CSI, X-Files and ER. When not pursuing his busy film career, he jumps on one of his bikes and blasts some of the "hollywood hype" out of his system. His bikes tend to be on the putbull side of things, loud, snarly and full of fight. Case in point his street legal XR750 flat-tracker.

Pitbull on wheels... Mike Bowen's streetable XR. Growing up in San Francisco, Mike and brother Bobby Carradine built their first bike, a 50cc mini-Honda which Mike, aged nine at the time, managed to immediately crash into a hedge but not before Bobby broke his arm trying to stop him. Both survived the initiation rites and moved up to bigger machinery. As a teenager, drawn into racing, Mike plastered his bedroom walls with posters of Alex Jorgenson's Ron Wood-built race Norton (which brother Bobby would go on to own), Kenny Robert's Yamaha, Jack Hatley's Triumph, and Jim Rice's BSA Triple. Call them his two wheeled icons. Some years later, inspired by watching Ascot half-miles and San Jose miles, Mike thought a Harley XR750 flat track race bike would be the ultimate street machine, and set about building just that.

His first XR was acquired from go-fast specialist Steve Storz, and says Mike, "Like my mini-Honda, I managed to blow-it to pieces. I delivered the basket case of shrapnel to Bobby who managed to rebuild the motor." The second XR project was turned over the legendary Mert Lawwill for a complete motor make-over. "I told him that I tend to get a little excited when I ride, so I wanted a motor that would hold together. As a result we decided to throttle back and go mellow rather than max."

"Like my mini-Honda, I managed to blow-it to pieces. I delivered the basket case of shrapnel to Bobby who managed to rebuild the motor."

Not only can you hear the XR a mile away, you can also smell the street legal flat track racer at some distance since Mike swears by Castor Bean oil, straight 40W, because it's "the only oil that goes toward the heat." He changes it every 600 miles, not because it breaks down, but because it suspends particles so well. "Any way, you want those particles removed frequently since the XR has no integral oil filter." It also feeds on 105 octane race gas, a liquid diet pretty much required by the 11.7:1 compression.  

Putting the V in velocity stacks. The engine itself took on a major transformation in the hands of the Mert. What first landed on his San Francisco workbench, the XR vee-twin was rated as a "junior" motor, but was returned as an "expert" class powerplant. Lawwill plugged in a set of Cosworth pistons topped off by specially prepped Axtell heads. Horsepower gains were the result of changing the cam timing and taking out the intake restrictors. Compensating for any loss of grunt caused by the reliability understressing, Lawwill added extra long intakes.  In effect, the engine was blessed with the best of both worlds, the excellent response at both low- and mid-range with plenty of go-fast at the top end as well.

The resulting rebuild produced a 750cc Milwaukee mauler that was owner-friendly as in somewhat under-stressed, yet still thrashed out a stout 88 horsepower. Fed by a pair of 38mm Del'Orto pumper carbs, this non-kick starter equipped XR requires a bump start. Fortunately, Mike, also a boxer, has excellent stamina. Mike also lives on a hill which helps, although Mike says, "You don't need a hill, just roll the bike back just past compression on one cylinder, at which point it'll turn over, then the momentum will carry it through a revolution at which time it will pop into life. No problem. I got the hang of it after the first two or three hundred times."

"The bike rides like the Bullet train on rails..."

Tipping the scales at a mere 335 lb., handling is further improved by Works Performance shocks, a Champion swingarm, and Marzocchi forks. Sun rims are laced with stainless spokes from Buchanan's, the wheels shod with a pair of sticky race compound Avon Super Venoms. "The bike rides like the Bullet train on rails," says Mike. Why go with a race bike for the street in the first place, and have to deal with no starter, no lights? Mike answers, "A lot of people take a street bike, and turn it into a race bike. I think that's the wrong way home. I think you should start with a bare minimum bike and bolt on the bare minimum to make it street legal. My goals were to make it light weight with sharp handling, good torque, with serious mid-range and reasonable top end." A room with a view...

Painting chores, including the Jack Hagman aluminum gas tank, were handled by paintmeister Tony Marcus who sprays many of the L.A. area high-end exotic bikes while Montrose Auto and Boat upholstered the seat. The trick footpegs, mirrors, headlight mount, and brake caliper hanger were fabricated by Don Nowell Design. The headlight itself is a spotlight that once served duty on a police car, an extra added feature Mike thought appropriate. The excellent results of Mike's effort are clearly audible thanks to the SuperTrapp stainless exhaust system fitted with racing tips. Lightweight, "sufficiently" powered and benefiting from "much improved handling", Mike's Pit Bull Harley is a major contender for baddest bike around. "I can give all those Angeles Highway Ducati riders a run for their money, especially on the tight and twisties," laughs Mike.


Flash and Crash: Evel Knievel's Death-Defying XR750

Evel was careful not to use fringe on his capes.He was a brash American cowboy, an outlaw on a Harley that broke the rules of gravity and logic to carve his place in his history. Yep, that bike stunt-riding guy in the Elvis-type costumes. He jumped bikes over fleets of buses and cages of tigers, and (almost!) jumped Idaho's three-quarter wide and 600-foot deep Snake River Canyon. It was to be the mother of all stunts.

Evel was going to leave Mother Earth, forsaking two-wheels for a fifteen foot long Harley-powered... rocket ship... the Skycycle X-1. The date was U.S. Independence Day, July 4th, 1973. The X-1 (yes, there was an earlier Bell X-1 experimental rocket plane that set records) was supposed to blast off from a 300 ft. ramp set on one side of the canyon, reach a velocity of 350 mph in eight seconds (which it did!), and then land by parachute on the other side. At least that was the plan.

In any case, Evel, a daredevil but not a dunderhead by any means, chose to replace the H-D V-twin with a Thunderbolt II steam rocket engine that pumped out 500 lbs. of thrust. The X-1 was supposed to blast off from a 300 ft. ramp set on one side of the canyon, reach a velocity of 350 mph in eight seconds and then land by parachute on the other side. Unlike an internal combustion engine with a whole bunch of moving parts, and thus more chance for something to fail at the wrong time, the Thunderbolt II had only one moving part. Seemed a good idea. Evel's sponsors were Harley-Davidson and Olympia Beer (always a good combination). Supposedly the only water pure enough to run in the rocket engine was the same pure water used in the beer, but that could have been pure hype, showmanship should we say, something Evel was a genius at producing. He was good, real good. To make a long, rather short story, shorter, Evel, after strapping on his good luck red, white and blue "Color Me Lucky" helmet was literally shoehorned into the cramped cockpit of the Skycycle. After lengthy preparations, someone lit the fuse, and Evel was off in a big flurry of flame and steam. He made it, well, part of the way, then bailed out with his parachute. Some say the ejection was way premature, but Evel stayed long enough to take the intense g-forces, strong enough to break one of his hips which had been surgically pinned after previous mishaps.

It was said that after so many bone-crunching spills, and resultant operations involving metal pins, Evel couldn't get within a hundred feet of a magnet... while his very real magnetic personality brought thousands of spectators flocking to his stunts. He earned and maintained international recognition as the premier death-defying crazy man for more than twenty years. The upside was that all the considerable pain gained him a measure of financial reward, purportedly six million dollars from the Snake River quasi-jump alone. (One of Evel's more widely witnessed accidents occurred on December 31, 1967 at one of Evel's nationally publicized events, a 150 foot fly-over of the Caesar's Palace fountains in Las Vegas. He cleared the fountains, but crashed hard upon landing, breaking his pelvis and a leg, but still went ahead with the Snake Canyon plans.) Dale Walksler on his Knievel XR at Wheels Through Time Museum.

Before Evel was riding rockets, he had a long association with land-bound Harley-Davidsons.

Towards the end of 1970, Evel signed a deal with H-D to ride the then-new XR750 Sportster in all his two-wheeled acrobatic displays of skill and "way-outness." Prior to this arrangement, Evel was already riding Harleys when jumping over cars and buses (lion cages, etc.), at least ten of them or a distance of 120 feet. Audiences, really waiting for him to splatter himself, ate it up. In June 1971, Evel was semi-immortalized by George Hamilton's portrayal of him in a film entitled "Evel Knievel," what else. It was pretty realistic except Evel never had as good a tan as Hamilton.

Evel transported his bikes in a very luxurious trailer-tractor rig complete with mahogany paneling and a whirlpool bath (and all of Elvis' big hits on the tape deck). He usually had three bikes set up for one stunt event; one for warm-up wheelies, another to show, the last to jump. The jump bike used a beefed up frame and rear section, and of course, a breathed-on engine. Wrenching on the chassis, race-tuning and such nuts and bolt work were not in EveI's job description: he was primarily an artist of speed and flight. While sensing every nuance of sound and feel of his bikes, he made certain that all components were coached to perfection since his life literally depended on it. This task he left to his chief tuner Roger Reimer, and when in California to experts like Steve Brackett. 

Looking for Evel in all the right places. The XR750 seen here (one of 200 made In '70-'71) was decked out in the "Color Me Lucky" decor by Evel's painter, George Sedlack (Moline, IL), and is now on display at the Wheels Through Time Museum in Magee Valley, North Carolina. Displayed with the bike are an assortment of Evel Knievel "collateral merchandise," including a lunch box, jigsaw puzzle, thermos, motorcycle model and even a juke box. Evel was a hot commercial commodity, a consummate showman, a lover of Wild Turkey whiskey, and, as heralded by the press, the "last gladiator" always in search of the optimum adrenaline rush. And he took a lot of fans along for the ride. Evel summed it up best when he said in an interview,

"In the stunt riding business, you have to make up your mind that you'll have to risk your life to get on top; and when you get there, you have to keep risking it to stay there." And he did.


Harley-Hybrid 1200 SportsterEast meets West with metric-Harley hybrid.

SoCal resident Steven Sites is a fan of the XR, dirt-tracking and the allure of transplanting the look of full-blown racer to the streets so he conjured up his personal vision based around a very modified 1200 Sportster motor and all the goodies he could find and then some. Can anyone out there in MO-land i.d. the source of the frontend? A clue... it's not from Milwaukee. Hint: we did say hybrid. Built some ten years ago, this feast for the eyes and soul is still food for thought for others similarly caught up in the magic of the XR.

*** 

Here are a few words from a rider who has known the XR since about day one.

Been There, Done That on an XR:

By Steve Matz --Here are a few words from a rider who has known the XR since about day one. Steve also graciously provided some of the photos for this article as well as the production numbers for the XR. Says Steve, "I had the very first alloy XR that came to Montana back then. The initial Dealer Cost for the XR was $ 2395.00 which the Dealer let me have at that Price. I sold the Bike to a Fellow that used it in a Joey Chitwood Type Thrill Show and used it to Jump Cars (like Knievel) As of a few years ago he was still using the same 72 XR in his Shows." "In the stunt riding business, you have to make up your mind that you'll have to risk your life to get on top; and when you get there, you have to keep risking it to stay there." - Evel

"Actually my affiliation with HD Racing bikes precedes both the Iron & Alloy XR. I had 2 KR Racers which were the 750 sidevalve twins used in AMA Racing from 1954-1969 I always tried to stay in touch over the years even when I wasn't attending races as to the changes and continuing R&D of the XR through the decades. Its longevity in AMA Racing (going on 32 years) far exceeds any other HD race bike ever built in HD's racing history."

"The motorcycle which produced in the area of 70hp in 1972 is now Producing in the Area of 105 rwhp on Grand National caliber race engines. The engine is still basically the same as what came on the scene in 72. It has received mods such as CDI Ignition, dual sparkplug heads, 12-1 CR, titanium valves, cam development, etc. that has made it possible to produce the current HP figures but the engines reliability has suffered as 21st century HP is still trying to be extracted from a 30+ year old design that wasn't intended to have the extreme limits of engine endurance it has to be subjected to. The XR is probably living on borrowed time as far as future sanctioned dirttrack racing goes but it is still the motorcycle that most of the fans in the grand stands come to see. Although noise standards at race tracks have made it a quieter machine than the old open megaphone racers from the 70's and early 80's, its sound is still distinctive XR."

"Jerry Branch of Long Beach, Ca (Branch Flowmetrics) ported and assembled all the alloy XR Heads and also the XR1000 street machine heads which were essentially the racing XR750 head. After his shop did the polishing and porting, assembly, etc., the Heads were air freighted back to Milwaukee and the Racing Dept. did final assembly of the engines."

"One thing that is noteworthy. The H-D engineers told Jerry to port the heads to specs they had come up with during R & D. Meanwhile Jerry had been doing his own testing and flowing of the head and actually had a configuration that was showing 3+ hp on the dyno more than the H-D configured design. Jerry offered to port the heads using his design for the same contract deal as the original. But the H-D people said, no, port them to our specs which he reluctantly did."

"Now when you got your XR and wanted more power you had to ship the heads back to Jerry and pay a few hundred dollars for a revised port job that could have been free in your original XR if H-D had swallowed their ego and went with the better ports that Jerry offered."

"Branch's XR engines consistently put out more power than the best factory race engines. Jerry was also the first to extract 100 hp from the XR engine even before the factory did. His rider Hank Scott, who won many Mile track Nationals on Jerry's equipment, had noticeable HP advantage over HD's factory engines. Branch could have also probably got the now defunct VR 1000 competitive in AMA Superbike Racing but again H-D engineer's ego got in the way and the project was withdrawn from Racing after humiliating results."

Steve Matz-BSP

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