Full-Blown Brick: BMW K100 Tracker

BMW K100 Custom

Ellaspede goes all-out on a Flying Brick…  

Introduced in 1983, the BMW K100 was a radical departure for BMW Motorrad, whose entire brand identity and heritage had been based on air-cooled flat-twin “airhead” motorcycles. In contrast, the K100 featured a liquid-cooled, fuel-injected four-cylinder inline engine with heavy design influence from the automotive world. Even stranger, the engine was laid on its side in the frame, leading to the bike’s “Flying Brick” nickname.

BMW K100 Custom

While Flying Bricks have become popular donors in the custom world, their boxy, even brutalist architecture makes them challenging to get right. Of all the many K100 customs that cross our desks here at BikeBound, only a fraction of them have lines and proportions that really work. However, this ’86 K100 from Brisbane, Australia’s Ellaspede instantly caught our eyes.

BMW K100 Custom

Ellaspede is one of the best workshops in world, and they understand the work required for a truly exceptional K100 custom:

“Their design is unmistakably unique and requires the owner to ‘go the whole way’ to make the most of the ‘Flying Brick’ look.”

BMW K100 Custom

Many builders utilize the Retro Rides horizontal rear suspension kit, but the Ellaspede crew opted to fabricate their own swingarm and linkage in-house, pairing it with a custom-fabbed chromoly subframe, quick-release seat pan, custom electrical box, and luggage loops for overnight trips.

BMW K100 Custom

Hughan from Ellaspede gives us the full rundown of the build below, but other highlights include modern Yamaha R1 forks with four-piston brakes, laser-cut aluminum side covers, LED lighting, and a Bates-style side spotlight that recalls the bikes from The Great Escape (yes, we all know McQueen and stunt double Bud Ekins were riding Triumphs disguised as BMWs). Says owner David:

“I knew that it would not replicate the old German bikes but that was the link to German engineering of the past. I was also posted to Germany for a while and had nothing but great memories of beer, Porsches and BMWs.”

BMW K100 Custom

Nicknamed “Kopfjäger” — German for “Headhunter” — this is one of the best-looking, most well-balanced K100 builds we’ve had the pleasure of featuring. Below, Ellaspede’s Hughan Seary gives us the full story on the build.

K100 Street Tracker: In the Builder’s Words…

BMW K100 Custom

The BMW K100 is a classic in the world of motorcycles. With its unique design, linear engine, and German engineering, it has stood the test of time and remains a popular choice among enthusiasts.

But as we’ve found with K-series custom builds, their design is unmistakably unique and requires the owner to “go the whole way” to make the most of the “Flying Brick” look.

BMW K100 Custom

One of the standout features of the K100 is its inline-four, 987cc engine. This liquid-cooled power plant delivers decent performance, generating a smooth and consistent power delivery throughout the rev range.

The frame, featuring BMW’s renowned “Flying Brick” architecture, offers good stability and balance. Combined with the engine layout, it gives the bike a distinctive look that sets it apart from other motorcycles of its era.

BMW K100 Custom

BMW has always been known for building durable motorcycles, and with proper maintenance and care, these bikes can easily cover high mileage without major issues, making them a reliable companion for long-distance touring or everyday commuting.

The K100’s exposed engine, riding stability, and renowned reliability are all big pluses for a custom build, but it’s the unconventional styling that seems to be the biggest stumbling block and in turn highest hurdle to doing a clean K100 custom.


Owner David gives us the backstory:

“I bought the bike at an online auction about 18 months ago. The idea was to have this as a slow project bike that I could work on, but I soon realised that the bike I had in mind was better built by professionals. Not sure of the history of the bike other than the original owner was also doing some resto work prior to me getting it.”

You can see in the original photo what David is referring to, with the previous owner stripping away most of the big BMW’s bodywork and fitting some small components. Unfortunately all of these parts except for the handlebars didn’t match the build, so they were swiftly removed before the new work began.

BMW K100 Custom

We’ve been a fan of the “Retro Rides” rear suspension kits for the K100’s, but they’re quite modern looking with their CNC construction, so on this build we opted to make something similar in operation but more closely matched to the factory frame style of the bike. The rear half of the frame was removed in favour of a chromoly subframe and horizontal suspension system that was designed and bent up in-house before being welded on.

BMW K100 Custom

A custom seat pan was fabricated with a quick-release latch and now matches the new rear frame, while a steel battery box was added to house the extensive electrical components found in the K-series. A steel inner guard was also fabricated to protect the electrical box and give the under seat area a nice clean look.

Finishing off the rear fab is an extended number plate mount that will also hold the tail light and indicators. Small “luggage loops” were also welded to the frame for securing a small pannier or an overnight bag for the longer excursions.

BMW K100 Custom

At the front, an upside-down Yamaha R1 front end was fitted with Cognito Moto triple trees and top bar mounts. The forks were sent off for refinishing and rebuilding before being slotted back in. They’re complemented by custom hub/disc spacers to accommodate the 310mm discs on the factory K100 front wheel, clamped by four-piston Yamaha calipers on both sides that were rebuilt and are fed through braided lines. A steel front guard was shaped up and hangs off custom “tubular” mounts from the bottom of the “upside down” forks.

BMW K100 Custom

Aluminium side covers were designed and laser-cut to fit in the frame triangle on each side below the seat. They feature K100 cutouts which were “back filled” with steel mesh for a contrast look and to stop anything unwanted getting in.

BMW K100 Custom

The K100’s engine, known for its reliability, had good compression and did not require a rebuild during inspection. It was removed and refinished in black, with the fins on each engine cover linished for contrast. Preventative maintenance was performed in the way of various engine seals, hoses, injectors, and components being replaced or refurbished as well. A special engine infill badge featuring David’s choice of German word “Kopfjäger” was also made in CAD and machined from T6061 aluminium.

BMW K100 Custom

Apart from wiring in new electrical components, finding suitable placements for all the necessary factory parts in a customised K-series BMW is a significant undertaking. The bike now features Daytona Velona 60 gauges for critical information display, controlled through custom Ellaspede K- series switches, and with turn signals indicated by Motogadget m-blaze bar end indicators at the front and Motogadget pin indicators at the rear.

BMW K100 Custom

A classic LSL headlight lights the way, with a neat Koso Hawkeye LED taking care of tail light duties out back. Daytona Rod D-mirror mirrors are underslung for the rear visibility.

BMW K100 Custom

The stock K100 headers were retained but shortened, a new 4-into-1 collector made and then connected to a shortened Supertrapp muffler mounted on a custom bracket.

BMW K100 Custom

The fabrication continued on a new radiator overflow bottle, foot peg mounts, a spot light bracket on the left hand side, repairs to the centre stand as well as the usual de-tabbing and cleaning of the frame and other components. A Bates-style spotlight now hangs off the left side with a replacement yellow lens to assist on the foggiest of early morning rides.

BMW K100 Custom

A new outer disc was fitted to the rear and the brake caliper was rebuilt and repainted to ensure it’s working correctly. A new YSS “black edition” rear shock slots into the new suspension mount to hold up the rest of the rear as well.

After completing most of the fabrication work, the bike underwent a thorough strip-down. Essential parts and components were sent off for paint, cerakote, or powder coat finishes. Shinko 712 tyres in 100/90-18 for the front and 130/90-17 for the rear were mounted on the factory K100 wheels.

BMW K100 Custom

The new seat was foamed up using a generous amount of high density comfort foam for the longer days in the saddle. Upholstery features premium black UV rated motorcycle vinyl with horizontally back-pleated across the top and bordered by a silver graphite stitch.

Getting to the paint, David explains his intended theme and colour choices:

“The colour came from the BMW Nardo grey and I thought that this would be a nice link to the present. I wanted the bike to remain true to its German heritage and so I was keen to enhance the BMW wording somewhere on the bike, which you can see on the front guard. This also led to the Kopfjäger reference on the engine side panel.”

“The original inspiration for a rambler style of bike (as opposed to a cafe racer) was the bike from the movie The Great Escape — hence the single side light. I knew that it would not replicate the old German bikes but that was the link to German engineering of the past. I was also posted to Germany for a while and had nothing but great memories of beer, Porsches and BMWs.”

BMW K100 Custom

Taking in David’s inspiration, we designed a classic colour scheme for the tank and front guard, featuring the BMW Nardo Grey with black “knee panels” on the tank and a metallic navy blue border and line work across both parts for a pop of colour. The extended BMW meaning also adorns the right side of the front guard.

When it comes to K100 builds, the philosophy followed here is to go all-out. The stock K100 can appear bulky and eccentric, so a half-hearted customisation attempt doesn’t usually result in a satisfying result. We think this build fully embraces the transformation, acknowledging that an impressive custom example of the K100 requires going the “whole hog” and we’re glad David trusted us to help him see it through.

BMW K100 Custom

Now that it’s finished, David says:

“It’s hard to say what my favourite part of the bike is as there is a lot to take in, but the rear suspension and swing arm looks incredible. I’m spoiled that I have a bike to ride to work and one for weekends. I joked that this one would probably end up inside as a feature piece, but my wife quickly shut that down. Not sure exactly with this one. Might use it to travel to bike shows or as a weekender.”

The BMW K100 is a classic motorcycle and if you ask us David now has a super clean example of a cool custom! With the smooth power, riding stability, and rad new looks we would take this thing for a weekend away any day, we’ll just have to convince David to loan us the “Kopfjäger” keys.

Follow the Builder

Website: www.ellaspede.com
Instagram: @ellaspede
Facebook: www.facebook.com/Ellaspede
Photography: AJ Moller (@ajmollerphotography)


  1. Elam Blacktree

    I would ride this. Best looking Brick I have ever seen. More, please!

  2. Other than putting decent front and rear fenders, and ride this bike, anytime. One can actually use the ergo triangle to be comfy. Well done.

  3. Clean, beautiful and useful. Very well done. A custom that can haul two people and some luggage with class… What a concept! Gorgeous build from one end to the other. Bravo!

  4. I’m a huge fan of the Ellaspede builds, and this one only further cements their reputation. This bike has balanced proportions, signature style, harmonising textures and colours, and real-world practicality. What else do you need? It’s the perfect ‘flying brick’. Congratulations!

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