Building a motorcycle with airplane engine sounds like something a mad scientist would do after one too many espressos in a drafty hangar. It’s loud. It’s heavy. It's honestly a bit terrifying when you're sitting on top of a machine designed to pull a Cessna through the clouds. Yet, this isn't just a niche hobby for people with death wishes; it’s a legitimate, albeit insane, engineering subculture that has produced some of the most mechanically fascinating vehicles on the planet.
You've probably seen the viral videos of the TMC Dumont or the Shrike. They look like they're from a Ridley Scott film. But underneath the chrome and the massive tires, there is a brutal reality to these machines. They are hard to ride, harder to build, and they represent a middle finger to the laws of power-to-weight ratios.
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The Reality of Radial Power
Most people think "airplane engine" and imagine a modern jet turbine. While those exist (shoutout to the MTT 420-RR), the purists usually go for radials. These are the circular, flower-shaped engines from the WWII era or small stunt planes. Why? Because they look incredible.
Take the Verity VBS. It uses a seven-cylinder Rotec R2800 radial engine. When that thing fires up, it doesn't sound like a Harley or a Ducati. It sounds like a warbird taking off from an aircraft carrier. The torque is massive. If you blip the throttle at a stoplight, the entire bike wants to rotate in the opposite direction of the crankshaft. That’s the gyroscopic effect at play, and it's enough to dump a novice rider right onto the pavement.
It isn't just about the noise. These engines are air-cooled by design, but they're meant to be moving at 150 mph at 5,000 feet. When you're stuck in traffic in downtown Phoenix on a bike with a 110-horsepower radial, things get hot. Fast. You’re basically straddling a giant space heater that’s spitting oil and screaming.
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The Engineering Nightmare of the Fuselage-on-Wheels
How do you even connect a radial engine to a motorcycle tire? You can't just buy a kit for this at your local shop. Most builders, like the legendary Jesse James or the team at Lucky 7, have to custom-machine every single component. We're talking about massive planetary gear reduction systems.
A plane engine spins at relatively low RPMs compared to a sportbike. While a Yamaha R1 might scream at 14,000 RPM, a radial engine is happiest chugging along at 2,500. This means the transmission has to be beefy. It has to handle torque that would snap a standard chain like a twig. Most of these bikes use heavy-duty shafts or massive belt drives.
And let's talk about the weight. A motorcycle with airplane engine isn't flickable. You don't "lean" into a corner on a bike that weighs 900 pounds with a massive rotating mass in the center. You sort of negotiate with it. You suggest a direction, and if the physics allow it, you turn.
Famous Examples That Actually Work
If you want to see who’s actually doing this right, you have to look at Henrik Toth’s "The Shrike." It’s a masterpiece of industrial design. Toth didn't just slap an engine on a frame; he built the bike around the aesthetic of a 1920s fighter plane. It uses a Rotec radial, and the attention to detail is staggering.
Then there’s the TMC Dumont. Built by former F1 driver Tarso Marques, it uses a 300-horsepower Continental V6 engine from a 1960s aircraft. It features 36-inch hubless wheels. It looks like a CGI render, but it’s real. It’s also incredibly impractical. The turning radius is about the same as a small moon, and the ground clearance is non-existent. But that’s not the point. The point is the "can we actually do this?" factor.
- The JRL Cycles Radial Chopper: One of the few "production" versions (if you can call it that) which used a Rotec R2800.
- The Leonhardt Gunbus 410: This holds the record for being the world's largest rideable motorcycle. It uses a 410-cubic-inch V-twin aircraft engine. It's over 11 feet long.
- Whitelock Tinker Toy: This one is just plain weird. It uses 48 cylinders from Kawasaki engines, but it’s arranged like a massive radial aircraft powerplant.
Why People Keep Building Them
Honestly, it’s about the soul of the machine. Modern motorcycles are getting too "perfect." They have traction control, wheelie control, and lean-angle sensitive ABS. They’re safe. They’re predictable.
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A motorcycle with airplane engine is none of those things. It’s raw. It’s a mechanical beast that requires your full attention just to keep it from stalling or overheating. There is a specific kind of person who wants to feel the vibration of a 7,000cc radial through their handlebars. It’s a connection to an era of aviation where everything was analog and dangerous.
The Technical Hurdles: Oil and Air
One thing hobbyists always forget: lubrication. Aircraft engines are often designed for "total loss" or dry-sump oiling systems that don't always play nice with the tilting and leaning of a motorcycle. If you lean too far, you might starve the top cylinders of oil.
Then there’s the fuel. Many older aircraft engines were designed for 100LL (low lead) aviation fuel. Running them on pump gas from the local Shell station can cause knocking, overheating, and eventually, a very expensive paperweight. Builders have to recalibrate carburetors or install modern fuel injection systems to keep the engine from melting itself into a puddle of aluminum.
Is it Legal?
Sorta. In many places, if it has two wheels, a headlight, and a blinker, you can register it as a "custom" or "constructed" vehicle. However, passing an emissions test with a 1940s radial engine is basically impossible. Most of these bikes exist in a legal grey area or are registered in states with very lax inspection laws. You won't see many of them being used for the daily commute to the office.
How to Get Started (If You're Brave Enough)
If you’re genuinely looking to build or buy a motorcycle with airplane engine, don't start with a scrap yard find. Aircraft engines have strict "timed out" lives. Once an engine has reached its flight-hour limit, it can no longer be used in a plane, but it's perfect for a bike.
- Source a Rotec Radial: These are the gold standard because they are still in production and parts are available. They are smaller and more manageable than a Wright Cyclone.
- Learn to Weld: You aren't going to find a bolt-on frame. You’ll need to master TIG welding and understand structural geometry to ensure the frame doesn't snap under the torque.
- Think About Cooling: Plan for electric fans. Unless you live in the Arctic, a stationary radial engine will overheat in minutes without forced induction.
- Budget for Failure: These projects often cost upwards of $50,000 and hundreds of man-hours.
The world of aircraft-engined bikes is a small, tight-knit community of brilliant, slightly crazy engineers. It represents the absolute peak of "because I can" mechanics. While they may not be the fastest bikes around a track, they are undisputed kings of the parking lot. Nothing else even comes close.
If you want to see these machines in person, your best bet is the Sturgis Buffalo Chip or high-end custom shows like the Handbuilt Motorcycle Show in Austin. Seeing a radial engine fire up in a bike frame is a sensory overload you won't forget. The smell of spent aviation fuel and the rhythmic "chuff-chuff" of the cylinders is something every gearhead should experience at least once.
To move forward with a project like this, your first step is researching "timed-out" experimental aircraft engines. Look for Rotec R2800 or Verner Motor radials, as these have the most documentation for ground-based conversions. Avoid salvaged engines from crashed planes unless you have the NDT (Non-Destructive Testing) equipment to check for hairline cracks in the crankcase. Focus on the transmission adapter first—connecting the engine to the rear wheel is where 90% of these projects fail. Secure a heavy-duty 90-degree gearbox or a custom primary drive before you even think about the frame.