BMW K 100 Blue Moon Has Futuristic Cafe Racer Cues Well-Suited to Its Sharp Angles

The abundance of positive feedback quickly made him consider switching to the bike-modding trade full-time, spurred on by Vera’s support at every step of the way. As Rusty Wrench (RW), it didn’t take long for them to establish a firm foothold in Portugal’s blossoming custom motorcycle scene. For a perfect example of what they’re able to pull off, we’ve the pleasure of introducing you to Blue Moon.

It’s a mouth-watering cafe racer with futuristic looks, based on a BMW K 100 RT from the model-year 1986. The K-series platform from Motorrad can hardly be considered an ideal basis for a cafe build, but it was a great fit for the aesthetic that RW had in mind. What’s more, we’ve seen a ton of airhead conversions done in this style, and it’s nice to see some builders bucking this trend with the liquid-cooled K models.

This particular specimen is a lot cooler than most, though, clearly showcasing the workshop’s incredible attention to detail. Once the Flying Brick had been delivered to their garage, a concrete design direction was established with the client and the real fun got underway. It started with a customary teardown and inspection, with all the original bodywork aside from the fuel tank getting eliminated in the process.

What came next was some intricate frame surgery, which saw the standard K 100 subframe replaced with a bespoke unit fabricated in-house. The new rear skeleton is topped with an incredibly stylish saddle, wrapped in two different types of premium upholstery and embellished with circular metal add-ons. Further back, there is a custom-built cafe racer tail section, but what lies underneath is even more enticing.

We’re referring to a snazzy taillight assembly put together with four vertical polycarbonate strips and bright LED internals. All this equipment rests on a high-grade YSS monoshock with adjustable preload, and the license plate is borne low down on a swingarm-mounted bracket. The billet aluminum rearsets placed a bit further ahead are one-off parts, as well, manufactured from scratch at the Rusty Wrench headquarters in Loule, Algarve.

Although the Beemer’s OEM gas tank has been retained, it was modified with a flush-mounted sport bike filler cap and RW badges that replace the BMW roundels. At the front end, we’re greeted by an LED headlight resembling that of a Harley V-Rod, encased in a handmade housing and held in lace via discreet mounting hardware. It’s placed in between a pair of upside-down Ohlins forks, along with a sporty front fender lower down.

The front suspension equipment is connected to the K 100 RT’s chassis with tailor-made triple clamps, and the headlight bucket continues upward to form a nose fairing of sorts. It surrounds a digital Motogadget dial, which is the only bit of instrumentation you’ll find on the Blue Moon. On the sides, the cockpit area is home to aftermarket clip-ons, featuring even more Motogadget paraphernalia.

It includes CNC-machined grips and bar-end turn signals, but one may also see a Domino throttle and Brembo master cylinders completing the package. Ample stopping power is made possible by Tokico calipers and drilled aftermarket discs at the front, while the stock rear-end equipment was kept and thoroughly refurbished. However, it is now actuated through a fresh Brembo master cylinder just like the front brake.

Opting to keep the original K 100 wheels, Rusty Wrench simply cloaked their rims in grippy Metzeler rubber on both ends. Once they’d rebuilt the donor’s inline-four engine wherever necessary, Francisco and Vera proceeded to add some juicy intake and exhaust tweaks. For the former, this involved the installation of a stainless-steel manifold, which breathes through a top-shelf air filter from K&N’s catalog.

Stainless-steel was once again the material of choice for the exhaust fabrication. RW came up with a neat four-one-two setup that ends in reverse megaphone mufflers on the left side of the rear hoop. Then there’s the simple, yet gorgeous paintwork adorning the Blue Moon’s upper garments – a mixture of black and blue contrasting rather nicely against the gold Ohlins forks and Tokico calipers.

Black is the predominant color everywhere else you look, applied onto the frame, front fender, and engine covers. There are some tiny pinches of red here and there, most notably on the switchgear, fork caps, and YSS shock absorber. Now, Rusty Wrench Motorcycles didn’t reinvent the wheel with this build, but they’ve certainly gotten the Flying Brick customization formula down to an art form!