David Song didn't set out to build the most talked-about custom motorcycle at Busted Knuckles Build-Off Season 3. He set out to build something genuinely different. He got both.
There's a certain kind of build that makes you stop mid-conversation and just stare. Desert Eagle, Moto Machine's entry into the 2026 Royal Enfield Busted Knuckles Build-Off, is that build.
It doesn't fit into a category. It doesn't look like anything else on the show floor. And when people saw it for the first time, they smiled. Not because it was pretty in a conventional sense, but because it was outrageous in the best possible way.
We sat down with David Song, the man behind the build, to find out how a Royal Enfield Shotgun 650 became a nitrous-equipped, post-apocalyptic desert machine inspired by Group B rally cars, Dakar racers and the imagination of a kid who never stopped sketching.
Who Is Moto Machine?
Moto Machine is Sydney's flagship Royal Enfield dealership. Walk through the door and it's immediately clear this isn't a generic multi-brand showroom. The fitout is purpose-built for Royal Enfield. The merchandise is there. The accessories are there. The range of bikes are there. Everything is pointed in one direction.
So when Royal Enfield Australia handed them a Shotgun 650 and said, effectively, go nuts, build us something for Busted Knuckles Build-Off, the team at Moto Machine had been waiting for exactly this kind of call.
"We'd seen the previous seasons," David says. "We always saw that and said, I wonder if we ever got that sort of call and challenge, what we would be capable of. We really wanted to find out."
The Brief: Do Something That Can't Be Pigeonholed
From the outset, the goal was clear. Don't build another bobber. Don't build another scrambler. Don't build something that a judge can file neatly into a category and move on from.
The problem? That's harder than it sounds.
"Bikes fall into certain categories because they have to," David explains. "In a car, you can make all sorts of shapes. As long as it can accommodate the seats within it, the car works no matter how strange the design. You could have an SUV or you could have a Ferrari. But with a motorcycle, the rider is integral to the bike. Those limitations always bring the design back to a kind of conformity."
That tension, between wanting to create something genuinely new and working within the physical constraints of a rideable motorcycle, became the central challenge of the entire project.
The Inspiration: Group B, Dakar, and a Car Guy's Design Language
David is, by his own admission, originally a car guy. And that automotive background is precisely what gave the Desert Eagle its distinctive character.
The early design references pulled heavily from Group B rally culture. Lancia Delta Integrales. Audi Quattros. That era of motorsport design is angular, aggressive, purposeful. Every surface means something. Form follows function in a way that ends up looking like pure art.
"I wanted to incorporate that angularity, that boxy rawness of early cars into this build. And it was fortunate that because of our lack of tooling, having to work with flat surfaces, those two things married together quite well."
By the midpoint of the project, the references had shifted slightly. Dakar racing machines had crept into the brief. That's where the ram air duct on top of the tank came from. A nod to the enormous roof scoops on Dakar-spec cars, translated into a motorcycle tank.
The Widebody That Didn't Make It
Here's the part of the build most people don't see: the ideas that got killed.
Moto Machine's original concept leaned into the widebody aesthetic of Group B cars. That hourglass shape, narrow in the middle, flaring out at the axles. On a car it works because the cabin geometry stays consistent while the bodywork fans outward. On a motorcycle, there's a fundamental problem.
"That section where the widebody starts is where you would be straddling the bike," David explains. "It's just too impractical. And because a motorcycle has one single tire, when you look at it from the front or the back, it looks outrageously thick."
From the side, the concept looked stunning in renders. From every other angle, it was unresolved. They 3D-printed elements. They mocked up shapes in cardboard. Eventually, they made the call.
Kill it. Start again.
"Those were the hardest moments," Song says. "We kept going back to the drawing board, and there were times we thought this might just be unachievable."
Working With What You've Got
Moto Machine is a dealership, not a fabrication shop. The tooling available for this build was, by professional custom motorcycle standards, modest. Bench grinder. Wire wheel. TIG welder.
Rather than letting that be a limitation, Song and the team turned it into a design philosophy.
"We had to be organic about how this evolved," he says. "In the beginning we tried the conventional route: here's a plan, work forward to achieve it. By midway through, we realised it was better to know what we couldn't do and work backwards from there."
The flat surfaces that the limited tooling demanded turned out to be the exact aesthetic the build needed. The constraints became the character.
The Ragtag Build Team
This wasn't a solo effort. The Desert Eagle came together through a network of friends, each contributing a specific skill to the whole.
David, Damien and Cam, from Moto Machine handled the build itself at the dealership. They had a mate come in for the CAD work and another for the welding for the elements that needed specialist hands. And because nobody at Moto Machine sprays, another mate was roped in look look after the paint work.
"It was the quintessential project bike," Song says. "People getting together, doing their bit, then coming together to form the whole."
Let's talk hardware. Because beneath the visual identity, the Desert Eagle is a serious piece of work.
The steel-fabricated fuel tank is the centrepiece. It is not a fibre-glass cover. It's a completely welded metal tank, hand-built, requiring a level of geometric precision that Song acknowledges pushed the team harder than almost anything else in the project. It only started to look right after the livery went on. Before that, there were moments of genuine doubt.
The custom aero wheel discs were, in David's own words, the moment everything changed. "As soon as we put them on, it balanced the whole bike. They changed the look entirely." The spokes are gone, replaced with a solid disc that bleeds into the blackness of the tyres and makes the wheels look like they belong on something considerably more intimidating.
The spec list continues: tank-mounted ram air intake, custom side-exit twin exhausts, three-row LED headlight setup, YSS rear suspension, NOS system, and a long list of fabricated, CNC-machined and 3D-printed components throughout.
The frame is largely untouched. That was deliberate.
"We wanted to build the custom Royal Enfield," Song says. "If you change absolutely everything, it could be any bike. But we wanted it to be recognisably a Royal Enfield. Just unlike any Royal Enfield anyone had ever seen."
The Name
There's a logic to calling it the Desert Eagle that's both obvious and brilliant.
Royal Enfield Shotgun 650. Built like a gun. Desert bike. Everyone knows what a Desert Eagle .50 calibre is. The naming writes itself. But beyond the wordplay, it embodies the spirit of the build. Fun. Loud. Unashamed. Not trying to be subtle.
"We've gone this far, there's no reason to give it a safe name."
People's Choice
When the votes were counted, the Desert Eagle took home the People's Choice Award at Busted Knuckles Build-Off 2026. Song's reaction?
Relief.
"Every victory, the greatest thing about it is relief," he says, citing a two-time MotoGP World Champion Casey Stoner line that landed properly when the award was announced. "When you're representing the brand or the dealership, you want to do it in a way that you're not letting anyone down."
The Expert's Choice went to the extraordinary RE1000 built by GRID Motorcycles, a world-first 1000cc Royal Enfield parallel twin hand-fabricated on the Gold Coast. Both awards found the right home.
But the People's Choice carries its own specific weight. Royal Enfield is a community brand. The Desert Eagle was always built for riders, not judges. Winning that vote validated the entire approach.
As for another Busted Knuckles entry, Song is open to it. But only when the idea earns it.
"We wouldn't do it again just to participate. We'd do it when we have an idea that resonates, not just with me, but with the whole team. Something we can all get behind."
Given what they built the first time around, that next idea is going to be something to see.
For the record, I asked David when I'd get a crack at riding it. He said anytime. Full disclosure: I am a 52-year-old whose idea of the perfect motorcycle is a Royal Enfield Meteor, so the Desert Eagle's aggressive riding position is going to test both my dignity and my chiropractor. We're doing it.
You can follow Moto Machine's builds and updates through their social channels. Desert Eagle is currently on display at their showroom.
Location photos by Tom Fossati and Moto Machine