"Birdcage" BMW by Revival Cycles

The Revival Cycles Birdcage BMW is one of the most audacious custom motorcycles built in recent years: a titanium lattice frame so open and intricate that the entire mechanical architecture of the bike is visible from every angle, cradling a prototype BMW boxer engine and revealing it as the sculpture it has always been. Unveiled at the Handbuilt Show in Austin, Texas, the Birdcage is Revival Cycles' tribute to the boxer engine that has defined an entire culture of motorcycling since BMW first introduced it decades ago.

Why the BMW Boxer Engine Deserves a Tribute

BMW Motorrad has been at the forefront of motorcycle engineering since its earliest days, and the horizontally opposed twin-cylinder boxer engine sits at the heart of that legacy. The design places the cylinders facing outward on either side of the frame, giving the engine its distinctive visual profile and its equally distinctive sound. Over the decades, the boxer became a cult object, drawing enthusiasts who valued not just its performance but its mechanical honesty: you can see how it works simply by looking at it. That transparency was the starting point for everything Revival Cycles built with the Birdcage.

The Titanium Birdcage Frame: Engineering and Inspiration

Alan Stulberg, head of Revival Cycles, looked to the birdcage-framed racing cars that Maserati and Porsche built in the late 1950s and early 1960s for the structural concept. Those cars used dense networks of small-diameter steel tubes welded together to create an exceptionally light yet rigid spaceframe. Stulberg applied the same logic to two wheels, creating what is believed to be one of the only birdcage-framed motorcycles ever built.

The result is a frame made from 138 individually cut, coped and welded titanium members. It was Revival's first time working with titanium at this scale, and the challenge was significant. "This was our first time to build a frame with titanium, that alone was already a significant challenge", Stulberg noted. "The frame came together very well in the end and we are very pleased with the result as it accomplished the goal of being nearly transparent." The contrast between the slim, almost ethereal titanium structure and the mass of the boxer engine beneath it is striking: the bulky engine sits at the centre of the composition like an exhibit, the frame a display case built around it.

Suspension, Componentry and Craftsmanship

Every component on the Birdcage was either fabricated in-house or specified with the same obsessive attention to detail as the frame itself. Lead engineer Chris Auerbach designed and built the front suspension around an Ohlins shock and a front control arm machined from CNC billet aluminium, with carbon fibre hexagonal tubing completing the assembly. The design draws on BMW's own tele-lever suspension geometry as a conceptual reference, then interprets it through Revival's handbuilt lens.

The handlebars and fork lowers reference the Ernst Henne land-speed record BMW racers of the 1930s, bringing a lineage of speed-record machinery into the frame of a contemporary custom. The engine and gearbox covers were fabricated from thin aluminium. Chief welder Ty Burham built a complete titanium custom exhaust. Titanium fasteners run throughout: axles, front suspension mounts, foot controls and footrests. The result is a bike that looks stripped back to the minimum, but reveals extraordinary complexity the closer you look at it.

Built in Under Six Months for the Handbuilt Show

The entire Birdcage project was completed in under six months, which makes the level of craft achieved all the more extraordinary. The bike was entered into the Handbuilt Show competition in Austin, one of the most respected gatherings of custom motorcycle builders in the world. For a machine that required designing and fabricating a first-of-its-kind titanium frame, sourcing and modifying a prototype BMW engine, and handbuilding every significant component, the timeline is remarkable.

The Birdcage is documented in detail on the Revival Cycles build blog, and it was covered extensively by Bike EXIF, the definitive publication for the custom motorcycle world.

Custom BMW Motorcycles and the Art of the Handbuilt Machine

The Birdcage sits at the extreme end of the custom motorcycle spectrum, but it points toward a broader culture of craftsmanship that TheArsenale has always championed. If the Birdcage represents the pinnacle of what a skilled team can do with a BMW boxer engine, explore the range of custom BMW motorcycles available through TheArsenale, including the BMW K75 Scrambler, the BMW R9T Gelber Baron, and the BMW R100 Scrambler #32. Our full motorcycle collection brings together the most compelling custom and production bikes from builders and brands who share Revival Cycles' commitment to the handbuilt ideal.