In the world of custom motorcycles, certain machines—the air-cooled Triumph Bonneville, the classic Honda CB, the BMW Boxer—are mainstays. They’re reliable, they’re beautiful, and they’re easy to chop up. Then there is the BMW K-Series.
Dubbed ‘The Flying Brick’ by those who loved its reliability but maybe not its aesthetic, the first-generation K-Series (K100 and K1100, 1983-1991) was a stark, rectangular block of Teutonic engineering. It was the antithesis of the curvy, traditional Boxer twin that BMW Motorrad had built its reputation on. And yet, this is precisely why it has become the darling of the modern custom scene.
It’s a machine that challenges builders to look past its chunky lines and find the sleek, high-performance heart beneath. The results? Pure, angular brilliance.
Today, we’re diving into our favorite custom K-Series builds from the ‘Flying Brick’ era. And for those keen to own a piece of this custom history, we have a pristine 1994 BMW K1100RS masterpiece, Kronos, currently up for auction on Bike EXIF Auctions.
Cardsharper’s BMW K1100LT Scrambler
Back in the 90s, the BMW K1100LT was a king of touring motorcycles, boasting the marque’s first engine over one liter, fuel injection, and a low-maintenance shaft drive. Compared to the competition, the K1100 was a technological tour de force—but all that came wrapped in a massive, heavy suit of bodywork. Jacek Mulak of Cardsharper Customs in Poland decided to drop that excess weight and transform it into something surprisingly sprightly.
Jacek’s client wanted a bike that could tackle country tracks and carry small luggage, steering away from the over-saturated café crowd. The resulting scrambler works surprisingly well. The aesthetic is dominated by brightly colored crash bars and a revised rear frame that flow perfectly with the stock tank—a feature often poorly executed on K-series customs. The rear luggage frames, which add a distinct charm, are removable, allowing for an easy change of style should the owner desire a café racer look later on.
The transformation goes far beyond aesthetics. The stock, low-slung muffler was replaced with new piping and an aftermarket muffler that terminates at license-plate level, eliminating a ground clearance liability. The wheelset is properly off-road friendly, sourced from a BMW R1150GS and refurbished into a classic F19/R17 setup. Even the cockpit, which on a BMW requires wrestling with complex electrics, was modernized with a discreet Koso TNT-04 ‘multifunction meter’ and a Motogadget keyless ignition, tidied up with a Maru Labs BEP3.0 conversion box.
The final touch? A stunning paint job with red tubing and yellow highlights that subtly evoke the spirit of Dakar—or perhaps the Moto Guzzi V85TT, as Jacek laughs. It’s a smartly executed custom that redefines what this three-decade-old machine can be. [MORE]
Vilnius Moto House’s K1100
The custom scene in Lithuania might be small, but it’s certainly deep underground. Case in point is this “angry, but exceptional” BMW K1100 café racer dubbed ‘Project #01’ from Vilnius Moto House (VMH). The challenge began with a simple client request, which escalated into a full-scale dismantling—a process VMH boss Darius Krasauskas describes as “very fast and without scruples”—to tackle the erratic factory lines.
VMH refined the chassis with a sharp, all-new subframe and a Yamaha R6 rear shock. The final, aggressive stance was set with a pair of unique 19-inch Harley-Davidson V-Rod solid front wheels, which required significant fettling and widening to adapt to the BMW’s single-sided swingarm. The custom bodywork is equally creative: after struggling with the OEM tank, they dug up a Kawasaki KZ550 unit, which was cut and narrowed to be the perfect match.
A unique touch is the custom fabrication around the engine, including a serpentine, four into one stainless steel intake manifold running off a single filter, complemented by a corresponding exhaust snaking under the motor. The lighting issue was solved with two long LEDs housed in a hand-made nacelle, with discreet Kellermann LEDs fulfilling the street-legal turn signal requirement. VMH’s hard work, which included two separate project stalls and a final three-week sprint to make the Custombike Show in Germany, paid off when the bike took top honors in the Roadster category. The monochrome spin on BMW’s traditional tricolor motorsports livery, executed with a cool, hand-painted feel, is a subtle but effective final note on this brutal build. [MORE]
VTR Customs’ K100 Endurance Racer
If the late 70s and early 80s were the golden age of motorcycle racing, the Swiss workshop VTR Customs is channeling that energy directly into their builds. Shop boss Dani Weidmann, a veteran of the endurance racing era, noticed the custom surge for ‘Flying Bricks’ and decided to pay homage to the classics with this stunning endurance-style street legal racer, aptly named ‘24 Hours.’
The idea was sparked at Spa-Francorchamps after watching a four-hour night race start with a Le Mans procedure. Dani’s vision was clear: double headlights with a removable “one-eyed” alloy race cover, a central rev counter, a Monza gas cap, and a definitive 1980s paint scheme. VTR kept the K100’s unique engine exposed to avoid it being mistaken for “another Japanese retro bike,” but tailored the bodywork by keeping only the upper part of a salvaged GSX-R750 fairing and adding vented side panels that match the tank’s lines.
The paint scheme is what truly sets it apart. After experimenting with orange combinations, the VTR team took inspiration from the Jaguar Racing F1 cars of the early 2000s. The green is an authentic match, and the classic race sponsors are replicated, with one clever twist: the HSBC bank logo was changed to ‘HSKC’ to reference Schmerikon, VTR’s hometown.
A titanium muffler, PVM three-spoke wheels, and a perforated Alcantara seat pad round out this beautiful endurance tribute. With its blend of German chassis, Italian exhaust, and F1 aesthetics, the ’24 Hours’ is a flawless tribute to a bygone racing era. [MORE]
Bolt Motor Co.’s K100RS
The BMW K100RS was already a statement when it debuted in 1986. But Spain’s Bolt Motor Co. saw the high-performance potential that lay beneath the geometric fairings of this ’80s-era machine. The result is a sharp, high-performing café racer, born from a client request that included a stunningly detailed, full-color sketch for the team to work from.
The focus was pure performance, which is no surprise since Bolt’s sister company is the Formula 3 racing team, Campos Racing. The team stripped the K100RS and injected race-spec DNA throughout. The engine received a custom-made intake canister, a relocated ignition, and twin Akrapovič mufflers connected to tweaked headers. The wiring was completely replaced with a Formula 3 racing-spec loom and Motogadget components. Shop boss Adrián Campos coyly mentions some other “fancy things” were done to the engine, but those secrets remain with the race team.
The chassis received an equally intense upgrade. The front end now sports Öhlins upside-down forks and twin Brembo brakes borrowed from an Aprilia RSV. This required machining all-new yokes and a steering stem. The rear features an Öhlins piggyback shock connected to a bespoke subframe, and even an Öhlins steering damper borrowed from the Aspar motorcycle racing team.
The finishing touch is an asymmetrical BMW M-inspired paint job, featuring the marque’s signature blue and red accents mirrored in the custom leather seat stitching. This bike is a testament to the fact that turning a client’s specific vision into a unique, high-end work of art is worth every man-hour. [MORE]
Empire’s Casino Royale
After years in the custom industry, Lithuania’s Two Wheels Empire was calling it a day to switching to e-bikes, and this brooding 1991 BMW K1100 RS café racer, dubbed ‘Casino Royale,’ was their stunning swan song. As the third and final ‘Flying Brick’ in their portfolio, it represented the “evolution of the species,” featuring the most expensive parts spec and aiming for near-perfection.
To achieve this, the team replaced the K1100RS’s bulky three-spoke wheels with refurbished, widened ‘octagon’ hoops from an older K100, now wrapped in Pirelli Angel GT tires. The front suspension is lifted from a 2017 Aprilia Tuono 1000 R, featuring Öhlins upside-down forks and twin Brembo brakes, held by Powerbrick Performance triple clamps. A custom-built Öhlins shock manages the rear. The bodywork is minimal, featuring a fiberglass tail section, a custom subframe, and the OEM fuel tank, all painted in Mercedes’ subtle Selenite Magno Grey.
The cockpit is finished with clip-ons, a Brembo master cylinder, and Motogadget components throughout. Signature touches include a K&N air filter, a unique four-into-one exhaust system with an underslung box muffler, and a subtle piece of artwork on the tank inspired by the original Ian Fleming Casino Royale book cover.
Though Matt, the shop founder, is moving to the electric world, he admits he would still be interested in making “one special K with an unlimited budget—an even more perfect version, one last time.” We sincerely hope he does. [MORE]
Electro Motorworks’ Electric K100
When Marshall Hewitt found a seized 1991 BMW K100 ex-police bike, he faced a serious challenge. Rather than rebuilding the seized engine, this automation engineer opted for a novel solution: yanking the internal combustion engine and replacing it with a modern electric powertrain. Marshall’s goal wasn’t just to get the bike running, but to maintain the “stock and iconic look of the K100 engine,” intentionally deceiving onlookers into thinking the bike was still a ‘Flying Brick.’
The deception is masterfully executed. Marshall 3D-scanned the original engine and designed a set of covers to accurately mimic the stock powerplant, hiding the new 35 kW electric motor and 8.2 kWh battery beneath. The bike is good for a top speed of 160 km/h (100 mph) in sport mode, with a claimed range of over 160 km (100 miles) in eco mode, utilizing the heavily modified, now single-gear, OEM transmission. A Motogadget ‘brain’ manages the wiring, tucked underneath the hollowed-out tank along with the charging system.
Marshall plans to offer this system as a kit under the banner of Electro Motorworks, focusing on a direct engine replacement that requires no permanent frame modifications. The rest of the chassis is equally impressive, with a rebuilt front end, de-tabbed frame, and a rear suspension system and subframe from Retrorides hooked up to a YSS shock. This K100 is not only a damn sharp-looking café racer, but a technologically stealthy platform that points to the future of custom motorcycling. [MORE]
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