Hot stuff: A brutalist BMW K100 street tracker from California

BMW K100 street tracker by Dunc Werks
We’ve all heard legends of the classic K-series BMW’s reliability, but the tale of this BMW K100 street tracker takes the cake. After all, how many motorcycles do you know that can set themselves alight, but keep on ticking?

The bike’s current owner, Duncan Bonar, found the 1985 BMW K100 at a local shop with a clean title —but there was a catch. “The only caveat was that it had self-immolated via an electrical fire,” he explains. “But hey, a bike’s a bike, and a clean title is a clean title.”

Based in Los Angeles, California, Duncan is an industrial designer who likes to tinker on bikes in his downtime. By day, he works as a designer at the popular dune buggy manufacturer, Meyers Manx. And before that, he was part of the team at the boutique motorcycle brand, Arch Motorcycle.

Although Duncan has recently queued up several project bikes under the moniker Dunc Werks, he started the K100 build several years ago with less urgency, working on it as and when he found the time. The K owes its brutalist aesthetic to Duncan’s industrial design background and his propensity for figuring things out as he goes. “This was an exercise in doing it yourself with the resources at hand; an ‘often wrong but never in doubt’ kinda mentality,” he says.

BMW K100 street tracker by Dunc Werks
Duncan’s first job was to get the K100 running after its little mishap. “The wiring harness, electric fan, and airbox assembly were all toasted. The motor and bike were quite caked with fire retardant, and there was a dent in the crank cover as the bike was dumped over at a traffic light when it decided to self-immolate.”

“Knowing that the K motors are relatively bulletproof, I wasn’t too worried about the internals. My bet paid off as no inner workings needed to be resolved—I just resealed and refinished the engine.”

BMW K100 street tracker by Dunc Werks
Once the K100’s eight-valve powerplant was purring again, Duncan could get cracking on the rest of the bike. Embracing the K’s inherently awkward lines rather than trying to ‘smooth’ them out, Duncan kept the OEM fuel tank and fabricated a kicked-up rear loop that matches the angle of the subframe. Next, he made the myriad aluminum parts that complete the bodywork.

“All of the aluminum parts were designed by myself with a set of calipers and CAD modeling software,” he tells us. “The laser cutting was outsourced to a third party, and then the bending was done by myself, using a manual bender.”

BMW K100 street tracker by Dunc Werks
The custom parts include the seat pan, which integrates the bike’s electronics tray and battery support, and acts as a rear fender. A row of LED lights sit at the back of the subframe, handling taillight and turn signal duties as needed. At the opposite end of the bike, a number board-style headlight nacelle hosts a Baja Designs light and a tiny digital speedo from Motogadget.

In the middle of the bike, you’ll find a small custom-made plate, designed to hide away the coils. Duncan embedded the ignition barrel into it too, and then added a manual fuel pump switch when he realized the space was missing something. “Flipping the extra switch gives the bike a more fun startup sequence,” he quips.

BMW K100 street tracker by Dunc Werks
Duncan pared down the BMW’s wiring harness, tweaking it so that he could use repurposed Kawasaki switchgear. The cockpit wears new Renthal handlebars; they’ve been bead blasted and clear anodized to give them a muted finish. Accompanying the Motogadget speedo is a custom-built warning lights panel.

Moving to the K100’s running gear, Duncan rebuilt the stock forks with progressive springs and fitted a new rear shock. The wheels and brakes are from a much newer BMW K1200, with custom axles, spacers, and brake caliper mounts accommodating them. The four-into-one exhaust is from BSK Speedworks—a race shop in the UK that runs K100s in endurance races.

BMW K100 street tracker by Dunc Werks
Duncan’s area of expertise is color and material design, so although the K100’s finishes are simple, they’re very deliberate. “I was looking for something that was undoubtedly classic, blurring the line between bold and reserved,” he explains.

“Land Rover and their more expressive colors of the past have always been near to this mark. The resulting color is a variant of Shetland Beige, which is kind of a warm putty color that compliments the Brick well.”

BMW K100 street tracker by Dunc Werks
Duncan opted to paint only the tank, leaving the aluminum parts raw to emphasize the concept of allowing the manufacturing process to lead the design. All the hard parts were powder-coated afresh, leaving this gnarly BMW K100 street tracker looking a lot better than the charred mess it was at the start.

Dunc Werks | Instagram | Images by Duncan Bonar

BMW K100 street tracker by Dunc Werks

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