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ADV BikesForm Follows Function On This Stunning Custom-Built BMW R100GS

Form Follows Function On This Stunning Custom-Built BMW R100GS

 Meet Gregor Halenda's vision of the ultimate BMW adventure bike.

Published on 03.04.2019

BMW R100GS Bike Build

Take a peek at this stunning, custom BMW R100GS. It’s sleek, poised and purposeful. It’s light and agile, yet tough and capable. It’s the kind of bike that could carry you to a rally from several countries away, through dunes and rocks and mud bogs, put up solid numbers in the race itself, then carry you several countries away again. It oozes old-school adventure as interpreted by a master craftsman.
It’s the bike BMW should have built at some point during the four-decade history of the GS, but didn’t. Enter Gregor Halenda and his BMW project bike. It’s an interesting story.

BMW R100GS Bike Build

Halenda is a professional photographer who started building custom bikes in 1998 after totaling his BMW R90S in a crash. He had just purchased a beautiful one-off polished aluminum fuel tank for it and didn’t want it to go to waste. A friend taught him machining and welding basics and he turned the bent BMW into a cafe racer that looked as good as it performed. Form and function had to merge on the project and that’s been the motivation behind his seven or eight builds since. One of his notable collaborations was the AWD KTM 950 Super Enduro built for REV’IT!. “My feeling then, and now, is that adventure bikes are the most relevant and interesting bikes to work with,” Halenda said.


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BMWs have been a passion for him since he was a kid. A neighbor’s R69S clocked 200,000 miles, which impressed him, and when Gregor’s father passed a few years ago he inherited his BMW with 294,000 miles on it. “[Older] BMWs are over built, simple and smartly designed,” he said. “I love the sound, the maintenance-free drive shaft and the look of the cylinders in the wind. They’re cool.”

BMW R100GS Bike Build

He first saw this R100GS on Bike-urious – a website that showcases unique motorcycles for sale. The previous owner, from Canada, modified the frame and built the tanks. Once again, it was the lovely polished aluminum tanks that started the wheels turning. “The tanks were the thing I loved most of all as they looked just like the sketches I’d done for REV’IT! but didn’t use,” he said.

A buyer from California snapped up the bike before Halenda could. A couple months later, Halenda followed up with the new owner to see how he liked it and learned the guy was having trouble getting it titled, and that there were mechanical issues. He sold it to Halenda.

BMW R100GS Bike Build

The bike turned out to be a bit of a heap. The engine burned a quart of oil every 100 miles, the brakes were marginal, the suspension worn out and the electrical system a mess. Even the tanks were more form than function: they leaked water into the fuel.

In the last year, Halenda has remade the bike top to bottom, front to back. He rebuilt the engine from the crank out, modified the frame to reposition the bodywork, machined a custom stem to fit the 450SX triple clamps, and swapped in 48mm WP forks from a KTM 690 Enduro R. The bike now sports over 11 inches of suspension travel, an increase from the previous 9 inches. The BMW also features Brembo calipers with custom stainless-steel brake lines. In the rear, he replaced the driveshaft, rear end and brakes.

BMW R100GS Bike Build

BMW R100GS Bike Build

Halenda’s decision to run a large 140/80-18 rear tire forced him to cut the swingarm apart and modify the mount. “I wanted to run Golden Tyre’s GT723R Rally Raid tires but in order to fit them, I had to cut apart the swingarm and machine a new mount out of billet and then weld this in. This mod took several days but allows me to run the largest wheel/tires ever run on a BMW,” explained Gregor.

The brake and shift levers are all custom fabricated with precision needle bearings and new linkages. And the tanks got attention as well: Halenda put in new petcocks, fuel necks and caps, and modified the mounts. Together, the three tanks hold a combined eight gallons (30 liters) of fuel.

BMW R100GS Bike Build

Fuel capacity speaks to the bike’s purpose: long-distance exploration without sacrificing high-speed, off-road fun. Halenda understood that achieving those often-contradictory goals in a single bike meant shedding as much weight as possible. That was factored into every design decision. The wheels, for example, were built by Woody’s Wheel Works in Colorado with lightweight in mind.

“The single most important thing to improve on is weight reduction,” he said. “I got the weight of this bike down to 400 pounds, with most of that weight coming off the wheels, the most important place to take off weight. Every pound of rotating weight is worth about three pounds of static weight. The wheels Woody’s Wheel Works made for me knocked off 20 pounds of rotating weight and the bike feels like its lost 100 pounds.”

BMW R100GS Bike Build

According to Gregor, the bike is now reliable and the handling is much quicker and lighter. “I have geared it down in the back with the lowest rear drive that BMW makes so the acceleration is pretty quick and the torque is really strong. Right now I’m working on the engine with the plan to get another 10 rear wheel horsepower out of the bike. This will give a good power to weight ratio.”

As well thought out, complete and beautiful as this R100GS is now, it’s really a test mule for Halenda’s next build, which he says will be “the ultimate BMW adventure bike, the bike my father would have wanted when he was 25 years old. Light, powerful, well suspended, simple and exceedingly beautiful. A bike you’d like to look at as you ride around the world.” Target weight on that bike is below 350 pounds, a goal he says is achievable by starting with a custom frame and lighter bodywork.

BMW R100GS Bike Build

“In my mind, adventure bikes are just as amazing a platform for a custom as anything; better in my mind,” says Gregor. When the next bike is fully developed, this one will go up for sale, he said, so stay tuned if you share his vision of what constitutes a great adventure bike. We’ll sure be following!

Halenda’s Custom BMW R100GS Mods

Base Bike: Mid 90’s BMW GS
Engine: Early 80’s BMW R100RS big valve
Head Work: Baisley High Performance
Body/tanks: Made by the previous owner from Canada
Frame: Cut, braced and the engine is raised and tipped
Driveshaft: R1100GS/R100GS hybrid
Swingarm: R1100GS cut, sectioned & shock mount repositioned with billet mount to allow 18” tire
Rear end: R850R 37/11 (lowest possible)
Brakes: Brembo
Suspension Travel: 11 inches (279 mm)
Forks: 48mm WP upside-down 2018 WP forks from a KTM 690R
Triples: KTM 450SX
Bars: ProTaper CR High
Wheels: Woody’s Wheel Works custom billet hubs, Superlight & Superlaced with two part disk rear hub laced with double butted spokes to Excell A60 rims
Tires: Golden Tyre GT723R Rally Raid in 90/100-21 front and 140/80-18 rear
Tubes: Tubliss
Grips Renthal half waffle
Shift/Brake: Handmade from 304 stainless on precision needle bearings
Footpegs: Fastway – adapted with custom hardware
Exhaust: 304 Stainless – handmade
Electronics/Ignition: Euro MotoElectric (EME) charging system and ignition
Dash/GPS/Gauges: Trailtech Voyager Pro

Photos courtesy of Gregor Halenda

Author: Bob Whitby

Bob has been riding motorcycles since age 19 and working as a journalist since he was 24, which was a long time ago, let’s put it that way. He quit for the better part of a decade to raise a family, then rediscovered adventure, dual sport and enduro riding in the early 2000s. He lives in Arkansas, America’s best-kept secret when it comes to riding destinations, and travels far and wide in search of dirt roads and trails.

Author: Bob Whitby
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2 thoughts on “Form Follows Function On This Stunning Custom-Built BMW R100GS

  1. Lovely and looks like a hoot! His next build sounds great! If he uses a HP2 as a base the weight reduction diet is going to be very interesting to see with a goal of less than 350 lbs.