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Battle of The Twins Redux: A 310-pound BMW race bike

Battle of The Twins Redux: A 310-pound  BMW R90/6 racer
In the lore of motorcycle racing, Battle of The Twins has few equals. First staged in the US at Daytona in 1981, the 50-mile series has spawned many epic duels—and spurred the development of the legendary Britten V1000.

The ripples from those thunderous early races are still felt today, as evidenced by this incredible BMW racer that just washed up into our inbox.

Battle of The Twins Redux: A 310-pound BMW R90/6 racer
It comes from classic race bike aficionado Scott Kolb, who’s based an hour and a half north of New York City.

Scott had a theory: “An air cooled BMW engine in a sweet chassis, with the right rider, just might beat up on modern sportbikes at local track days.” He set out to build a 310-pound [140 kg], 82 horsepower track bike.

Battle of The Twins Redux: A 310-pound BMW R90/6 racer
Influenced by the writings of Tony Foale and the race bikes of Chris Hodgson, Scott decided to build a homage to the great Daytona BoTT racers. So he pulled the engine from his 1976 R90/6 road bike and put the rest of the machine on eBay to help pay for parts.

Fortunately, he had a client with the same vision. And like Scott, the client works in the high-end architectural field, and he is a hands-off kinda guy.

Battle of The Twins Redux: A 310-pound BMW R90/6 racer
“We’ve both seen enough clients ruin great design by diluting the original vision,” says Scott. “The best projects come from a consistent and pure design idea.”

“To that end, he offered no commentary—not even about color. But he did say ‘The bike needs to fit me,’ and left it at that. He’s 6′ 4″ and 240 pounds, [109 kg] so I made a bike to measure.”

Battle of The Twins Redux: A 310-pound BMW R90/6 racer
Like a good suit, this BMW fits him to a tee. For starters, both the wheelbase and the ergonomic triangle—pegs to bars to seat—are 5% bigger than the average production bike.

This is second nature for Scott, because the many chassis he has built over the last 20 years have a strict focus on function—while being mindful of the need for visual flow.

Battle of The Twins Redux: A 310-pound BMW R90/6 racer
Scott knew that the target weight figure would require carbon wheels from Rotobox and Öhlins R&T suspension front and back. The carbon wheel is only available for the BMW R nineT, which prompted Scott to use other R nineT parts like the rearsets, levers, blinkers, mirrors, and a license plate carrier from Rizoma.

Rizoma uses surface machining on many of their parts, which shows in the machining flowlines left behind by the ball mill cutter. I love this look: it adds a little texture for a good feel under your glove, plays with light, and most importantly shows the thought process of the CNC programmer—giving the parts a human touch.”

Battle of The Twins Redux: A 310-pound BMW R90/6 racer
The engine has all the classic go-fast bits offered in the mid 80s by Chris Hodgson’s CC Products outfit (which has now morphed into San Jose BMW). The heads are dual-plugged, with larger valves and porting and flowing. There’s a lightened and balanced flywheel, a performance clutch, and a crank dynamically balanced by Falicon. Displacement has been bumped up to 1000 cc using the well-known Siebenrock big bore kit.

“A 200-section rear tire was completely unnecessary, but I couldn’t resist!” says Scott. This required a one off swingarm with extra offset, and a lot of machining to get the R nineT rear drive to mate up to an airhead transmission. The Brembo calipers are from a BMW S1000R, matched to Brembo master cylinders, and the clutch is a hydraulic setup from SWT-Sports in Germany.

Battle of The Twins Redux: A 310-pound BMW R90/6 racer
The 4130 chromoly tube chassis is based on the famous ‘Team Incomplete Boxer’ owned by photographer Gregor Halenda, but goes one better.

It includes a similar motor mount that attaches to the top of the engine block, and eliminates the cradle downtubes. “This visually frees up the wonderful cast block that we all love,” says Scott, “but the real benefit is quicker lap times.”

Battle of The Twins Redux: A 310-pound BMW R90/6 racer
The powder-coated tubing is a thing of beauty, and the ‘one better’ part is a rear billet mounting block to eliminate the tubes reaching to the bottom rear of the engine block. “While we were at it, we realized we could isolate the forces of the rear swingarm from the front end by making the swingarm pivot in its own subframe.”

The bodywork was styled in-house. “It’s simple shapes, found by laying lines over photos of the rolling chassis,” says Scott. “The actual shapes were formed by sculpting foam, and then molds were made.”

Battle of The Twins Redux: A 310-pound BMW R90/6 racer
The fairing and seat unit were were laid up in carbon fiber, with the outer layer being a 3oz twill weave. (“I like how the asymmetrical weave gets the compound curves to really pop.”) The tank was hammered out of .062 aluminum, and is finished with a Rizoma fuel cap.

The technology may be modern, but the body finishes have a hint of retro style. “I love 70s graphic design,” says Scott. “Primary color schemes were everywhere when I was a kid, and seem to influence my company’s aesthetic choices.”

Battle of The Twins Redux: A 310-pound BMW R90/6 racer
“A pure cyan is used on my company logo, and always seems to make it into our race bikes. Throw in the Öhlins gold and Rizoma’s red accents, and you have a bike ready for the full primary color treatment—which lead to the red stripe down the center of the body, splitting the carbon and aluminum.”

The electronics are ultra modern, with a Motogadget m.unit control box at the center, taking signals from discreet m.buttons and a keyless ignition system. “The keyless receiver is hidden in the carbon fiber seat unit, along with all of the electronics,” Scott reveals. There’s a new ignition module too, from Euro MotoElectrics.

Battle of The Twins Redux: A 310-pound BMW R90/6 racer
The BMW hits the 310-pound, 82 horsepower target, and Scott has finished it just in time to ship it to the One Moto Show at the Veterans Memorial Coliseum in Portland, Oregon, which opens on February 7.

Once he gets the bike back, it’ll be fettled and tuned for the track, and ready for informal battles with more modern sportbikes. It’ll be intriguing to see how it fares.

Battle of The Twins Redux: A 310-pound BMW R90/6 racer
In the meantime, enjoy these images by Gregor Halenda, who has become a friend of Scott’s since the days of the Team Incomplete BMW build.

Battle of The Twins Redux: A 310-pound BMW R90/6 racer

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