Tech Tuesday: H-D Screamin’ Eagle Road Glide Special

Resplendent in its Evel Knievel/Mert Lawwill-esque #1 is defending Mission King Of The Baggers Champion Kyle Wyman’s H-D Screamin’ Eagle Road Glide Special next to current KOTB Championship leader Travis Wyman’s identically prepared Bagger racebike. Photo by Brian J. Nelson.

Other than trying to win races, MotoAmerica teams and riders are constantly developing their motorcycles. It’s a task that never ends, whether it’s simple suspension settings like front suspension preload, front or rear compression or rebound damping, ride height, or more complicated things like engine braking, fuel, or ignition mapping, depending on the race class and the rules for that class.

The lion’s share of development occurs in MotoAmerica’s Medallia Superbike class, but the two race classes that are a “tuner’s dream” are REV’IT! Twins Cup and Mission King of The Baggers. The rules in those two classes provide a lot of latitude for developing motorcycles.

An H-D Screamin’ Eagle Road Glide Special test mule with an earlier version of the in-house engineered and fabricated swingarm and chain tensioner. Also note the additional idler sprocket attached to the top of the swingarm. Later versions of the swingarm and chain tensioner eliminated the need for the additional idler wheel. Photo by Brian J. Nelson.

In Mission King Of The Baggers, the development “curve” in the past two-years-plus-one-race has resembled the face of Yosemite National Park’s El Capitan. In other words, straight up. Not only have the lap times dropped by more than five seconds at almost every racetrack this season compared with the 2021 season, but the engineering and technology incorporated into the Harley-Davidsons and Indian Challengers have been breathtaking to witness.

Taking a closer look at Kyle Wyman’s and Travis Wyman’s H-D Screamin’ Eagle Road Glide Specials reveals interesting components, parts, and pieces not only from one end of the bikes to the other but also from one side to the other.

For this story, I concentrated only on the middle two-thirds of the left side of the bikes.

The rear-cylinder-cooling carbon-fiber ram-air scoop on Travis Wyman’s Road Glide Special racebike. Photo by Brian J. Nelson.

First off, the Road Glide Special is mostly an air-cooled V-Twin motorcycle. I say “mostly” because the bikes feature a nifty little system called “Twin Cooling” that provides liquid cooling to only the exhaust valves on the bike. There is a small water jacket around the exhaust valves that is plumbed to a pair of radiators. Twin Cooling is an OEM feature that is incorporated into the Wyman Brothers’ racebikes.

OK, now that I’ve gotten that detail out of the way, and since the bikes are, again, mostly air-cooled, the rear cylinder of any air-cooled, in-line, V-Twin engine naturally runs a little bit hotter since it’s blocked from the oncoming air stream by the forward cylinder. Harley-Davidson’s simple, yet brilliant, solution is a carbon-fiber ram-air scoop that funnels air directly at that rear cylinder.

The left two-thirds of Kyle Wyman’s championship-defending machine. Note the carbon-fiber ram-air scoop, 3D-printed “pommel,” gearshift lever and linkage, primary-case-mounted left footpeg, beveled primary case with case guard, spring-loaded chain tensioner, and CNC-fabricated swingarm. The red “R” in the “131R” on the sidecover stands for “Race.” Photo by Brian J. Nelson.

In a perfect execution of form follows function, Harley also created a swingarm that is an absolute work of art. But, more importantly, it shortens the wheelbase of the racebikes, helps facilitate the much higher ride height of the racebike compared with the stock street-going Road Glide Special, and whose intricate webbing delivers the desired reduction in weight without compromising strength or structural integrity. Leave it to the CNC-machining wizards at Harley to create such an equally beautiful and functional piece.

The spring-loaded chain tensioner is also a technical manifestation of “form follows function.” Appearing like jewelry or a sculpture on the left side of the Wymans’ racebikes, this spring-load mechanism was engineered to maintain constant tension of the chain despite the fact that the front sprocket and swingarm pivot are radically askew from each other due to the downward angle of the swingarm necessitated by the dramatically increased ride height of the bike. It’s technology derived from some dirt bikes—with their ultra-long suspension travel—and it works beautifully for these Mission King Of The Baggers Harleys.

There are so many other trick pieces on the Wyman brothers’ racebikes. The 3D-printed “pommel” attached to the top of the gas tank that helps Kyle and Travis hang off their bikes in the corners. The machined-from-billet-aluminum primary cover with the integrated left footpeg bracket that provides the ideal ergonomic position for the rider’s left foot. The beautiful and elaborate shift linkage. The list of eye candy goes on.

And that’s just the left side of the H-D racebikes.

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