Shogun FMX Bike
Background
The Shogun FMX Bike came from years of competitive freestyle motocross experience and continual bike refinement. What started as normal setup changes and small performance gains eventually became a larger engineering problem: how do you build a motorcycle specifically for FMX rather than continue adapting a motocross bike for a job it was never designed to do?
By that point, conventional modification had reached its limit. The remaining constraint was the chassis itself. The geometry of a motocross bike does not fully suit freestyle motocross.
The clearest comparison is bicycles. Downhill bikes, cross country bikes, road bikes, and dirt jump bikes all use very different geometry because each discipline demands different handling characteristics. Dirt bikes are no different. A motocross bike works well for FMX up to a point, but once the sport progresses far enough, the limitations become obvious.
For the first 20 years of FMX, riders had not yet fully outgrown the available bike technology. The same thing happened with ramps, which is why we developed and released the Next Gen ramp in 2017. The bikes needed the same level of rethinking.
This project was the result of that process.
The design goal was simple: build the best FMX bike possible while keeping it dependable. The bike needed to be agile in the air, easy to move around, and easy to spin. To achieve that, chassis geometry was the priority, followed by reducing rotational mass, centralising weight, and then reducing overall weight.
Engine
The bike uses a KTM 250 SX engine from the 2017 to 2022 generation. In our view, this is the peak KTM two stroke engine platform. The engine was completely disassembled and rebuilt from scratch.
The transmission was converted to single speed. In FMX competition, second gear is used almost exclusively, with third gear only used rarely. This bike was built specifically for regular FMX ramps in the 45 to 75 foot range, so all gears other than second were removed. Unused gears were physically removed and machined off the shafts, with spacers added where required.
All bearings were replaced with ceramic bearings to reduce friction and save weight. All fasteners were replaced with titanium. Other steel components were remachined or 3D printed in titanium where appropriate. The cylinder was ported and the port heights set to suit the intended timing. The head was machined to achieve the target compression ratio. The cylinder and head specification came from years of previous testing.
Total engine weight reduction was 2.2 kg, or 10 percent.
The single speed transmission delivered several advantages. It reduced overall weight, reduced drivetrain losses, and most importantly reduced rotational mass. That reduction in rotating inertia made a major difference in the air. The bike whips and spins more freely and with less effort.
Intake
The air intake boot was designed from scratch. We retained the same volume as the standard 250sx intake but redesigned the shape to suit the application and available space. It needed to package around the shock, fuel tank and bodywork while still delivering the required airflow.
The part was SLS printed in nylon filled with fiberglass. This material was chosen for stiffness and chemical resistance. The increased stiffness of the intake also improved throttle response.
Exhaust
The pipe and silencer were completely redesigned and rerouted to improve mass centralisation and left to right balance.
The target for the bike was 50/50 side to side weight distribution and 50/50 front to rear distribution. Side to side balance is particularly important in FMX. If the bike is not balanced laterally, it will rotate more easily one way than the other during whips and spins.
The exhaust pipe was routed up through the area normally occupied by the left radiator. The silencer was then routed to the right side of the bike and down alongside the shock, with the outlet exiting behind the rider’s boot.
The pipe was made from stainless steel. Titanium was considered, but it would have changed the pipe characteristics significantly and introduced another major development variable. Stainless was the better choice for function, repeatability, and practical build time. It was also more suitable given how exposed and damage prone the pipe is in this application.
Custom press tools were designed and CNC machined from steel to form the pipe sections. The silencer was made from titanium and carbon fibre, with 3D printed titanium end caps and a carbon fibre body.
Fuel Tank
The fuel tank is centrally located in the bike and was SLS printed in nylon fiberglass. Its position was critical to the overall mass distribution of the chassis. Relocating the fuel mass from the upper part of the motorcycle to a central position made a significant difference.
The tank includes a sight feature so fuel level can be monitored visually. The breather routing was also designed specifically for FMX use. It runs around and down from the tank so the bike does not leak fuel when upside down or when used in a foam pit. The breather is not attached to the filler cap, which makes refuelling easier. The tank also incorporates heat shielding to reduce temperature transfer from the engine.
Frame
The frame is the key part of the bike.
It was built in chromoly. Titanium and carbon fibre were both considered, but this bike was designed to be ridden and proven, not built as a concept piece. We wanted a material we trusted structurally while remaking almost every part on the bike. Now that the design has been proven, those material options could be revisited in future.
The frame is actually heavier than a regular KTM 250 SX frame. While not intentional. The objective was function and durability, not making a fragile showpiece. The twin spar design was necessary to centralise the mass and package the tank, shock, and silencer in the centre of the chassis.
The frame uses CNC machined, 3D printed, and laser cut components, TIG welded together with chromoly tubing. The lower rails hug the engine closely to centralise mass. The down tube is CNC machined in two halves and welded together, allowing it to be kept extremely slim for front wheel clearance at full compression.
The geometry is completely unique and significantly different to a KTM 250 SX or any conventional dirt bike. The engine mounts are also custom designed and CNC machined from 6061 aluminium.
Steering Damper
The steering stabiliser is integrated into the frame and uses a linear style damper rather than the conventional rotary type used on motocross bikes.
A linear damper was chosen because it can operate at much higher damping levels and offers significantly better service life. At the peak of riding, a conventional rotary damper would need rebuilding weekly. This linear unit has not required that level of maintenance.
The damper mounts directly to the frame and links to the triple clamp through a custom designed linkage. It also uses a custom 3D printed aluminium adjustment dial for easy access. All associated clamps, mounts, and components were custom designed and machined to suit the chassis.
Bodywork
The objective was for it to be light, visually light, and highly open to airflow. The open design was intended to reduce the effect of side wind and head wind on the bike in the air.
The front fender was designed specifically with head wind effects in mind. In strong head winds, a conventional front fender can lift the front of the bike. This fender is shorter front and rear and incorporates vents in both the main and rear sections. It was laid up with Soric core in selected areas to add stiffness without unnecessary weight.
The front number plate is small and slim to improve foot clearance during tricks such as cliffhangers. The cable is retained with a 3D printed nylon carbon fibre clamp. The front fender and number plate are mounted with aluminium fasteners to save weight. They are not as strong as titanium, but in this application that is acceptable.
The shrouds are very light and designed for simplicity and airflow.
The centre body section is a structural component and part of the two piece subframe. It uses a 3D printed foam style core for shape and support, along with CNC machined inserts for fasteners. This section supports the seat and connects the rear fender to the lower subframe and side panel structure. It is intentionally open to improve airflow and give the rider multiple grab points.
The seat is slim, and because there is no fuel tank in the conventional position, there is substantially more foot clearance at the front. The seat foam was originally moulded, but later changed to a 3D printed TPU lattice structure to reduce both weight and labour.
The rear fender is extremely light and integrates into the subframe structure. The lower side plates are also structural. They are slim and open to minimise wind effect. The side plate grip sections are 3D printed and provide boot grip, which is an important control point during flips and spins.
The fork guards are also custom designed, shorter than standard.
All carbon fibre parts were resin infused and produced using custom designed CNC machined billet aluminium moulds.
Suspension
The suspension is WP, using air forks and a PDS shock.
Selected steel internals and a small number of fasteners were remachined in titanium. The forks were shortened by 25 mm to suit the intended chassis geometry. Rear wheel travel was matched to the front.
The suspension was tuned by Renny at The House of Dirt. For the forks, we used the setting already developed and proven on the previous bike. The rear was developed specifically for this chassis. An initial setup was tested, revised, and then left unchanged after the second iteration.
Outcome
The final wet weight of the bike is 81.6 kg, or 179.8 lb. That figure is wet, not dry.
When this process started, the competition bike being ridden weighed 105.8 kg, or 233.2 lb. This bike came in 24.2 kg lighter, which is a 23 percent reduction.
Weight was a major objective, but geometry was the primary one. Fork angle, rear wheel position, footpeg position, and bar position all play a major role. The final bike achieved 50/50 front to rear and 50/50 side to side balance.
On the bike, the results were clear. Throttle response was sharper, pickup was stronger, and the reduction in rotational mass made the bike noticeably easier to move in the air. It was stable, balanced, and particularly strong in windy conditions. The aerodynamic theory behind the bodywork translated into a real result when ridden.
The bike also rotated extremely easily on flips. Even well past peak riding years, it was capable of bigger tricks with less effort and faster rotation than a conventional setup.
From initial design to first ride, the project took two years. That included approximately 18 months of design development and prototyping, followed by six months to complete the final build.
Once the bike had been designed, built, and proven, it became clear that the project had done more than produce a motorcycle. It shaped the way we approach design, engineering, and fabrication at Shogun today.
Conclusion
The Shogun FMX Bike was built to solve a problem: a motocross bike is not an FMX bike.
This project was our answer. Every major system was reconsidered through the lens of weight, balance, geometry, serviceability, and real riding performance. The result was a purpose built FMX machine that was designed, ridden, and proven.
Only two Shogun FMX Bikes were built. The first, VIN SGI001, became Levi’s personal bike. The second, VIN SGI002, was built for close friend Dean Graham and now sits in his private collection of bikes and cars in Christchurch.
A small run, built with purpose, and a project that represents exactly what Shogun is about.