FX Bikes

FX Defense – Super-Lightweight Motorcycles for Military and Relief Applications

FX-4 Military Motorcycle Concept

FX-4 Defense Concept by Virtual Simulation Systems

FX originally saw the Mountain Moto as a defense product, but for a number of reasons we have decided to focus on the off-road and dual sport/recreation markets at first.

However, if “friendly” military and relief organizations are interested in our commercially produced models, we’re happy to talk, in defense language of course, using plenty of serious words like gradeability and TLAs (three letter acronyms)…starting with a new name…SLM.




World’s lightest performance off-road motorcycle: 132lb (60kg) ready to ride

  • US Marines KLR250 Gasoline: 250lb (115kg)
  • US Marines KLR650 Diesel: 390lb (180kg)
  • SLM mobilizes one operator with 90lb (40kg) pack and equipment
klr650 diesel military motorcycle lineup

US Marines KLR650D

Defense evaluation and testing in NZ and USA to date

  • Series of trials by NZ Army at Burnham (see below)
  • Informal trials by NZSAS, US Navy SEALs, Singapore Army (all Special Forces)
  • Request for quotation to supply test units to US Army

Key advantage – mobility in difficult, tight, broken terrain

  • Ride, walk, manhandle, lift over otherwise-impassable barriers
    • Mountain/forest singletrack, fallen trees, fences, riverbanks, urban rubble, etc.
  • Reconnaissance and Special Operations seen as primary defense applications
  • Teams with tight space constraints that need ground mobility above walking
    • Air crew and ground support troops in a field environment, naval shore parties

klr650 stuck in mud

Other advantages – portability and usability

  • Carry on other light to medium vehicles e.g. LAV, LOV, SOV, assault boat/RHIB, UH-1/A-109/NH-90 and most other helicopters with a cargo/passenger compartment
  • Pack into larger vehicles for easy deployment e.g. medium lift vehicles, C-130, P-3K, Inshore Patrol Vessel, Offshore Patrol Vessel
  • Maximum use of stock commercial parts, designed for ease of maintenance, minimal training necessary for field or workshop maintenance.
  • Auto-clutch option, lightness and low seat mean extreme ease of use – low training requirement; low accident rate
ktm crash
Higher Accident Rate on Conventional Motorcycles

SPECIFICATIONS (subject to change and to modification to meet user requirements)


  • 132lb (60kg) ready to ride


  • Acerbis street legal lighting as required; 6V/12V jacks for helmet lights and equipment charging


  • Excel motocross rims; Michelin motocross tires

Air Filter

  • Standard motocross foam filter in sealed airbox

Seat Height

  • 31” (800mm)


  • 350lb (160kg) total; 260lb (120kg) rider + 90lb (40kg) pack & equipment


  • Rifle rack/scabbard, pack racks, anchor points etc. to required specifications


  • Climb/descend/traverse slopes up to 45o

Fording Depth

  • 24” (600mm); easy to restart if waterlogged; floatable on portable inflatable device e.g. inner tube

Turning Radius

  • 5′ (1.5m) minimum space required to turn 180o(able to pivot on rear wheel or lift and turn)

Lifting Height

  • Single operator can lift over 4′ (1.2m) obstacle; 2 people 6′ (2m) e.g. truck deck (typically 6 people to load a KLR250 onto a Unimog)

Max Speed

  • 125cc 60mph (100km/h); peak performance 20-40mph in difficult terrain; 250cc est. 80mph (130km/h)

Packed Dims

  • L: 48” (1200mm); H: 36” (900mm); W: 16” (400mm) with front wheel and handlebars unbolted

Packed Weight

  • 200lb (90kg) in air/sea/container crate

Fuel Tank

  • Fire/explosion-resistant

Gasoline Models

  • Standard Engine (recommended, plenty of torque and power to carry full payload up steepest grades): 125cc 4-stroke gasoline, 4-speed, auto-clutch (recommended) or manual transmission*
  • Higher Capacity Engines: 150cc and 190cc available from Daytona Japan, auto-clutch option would require short term development, yet to be durability tested in SLM package.  250cc engines require longer term research and development.
  • Fuel Range:  3 gallon (12 litre), up to 360 mile (600km) range (approx. 120mpg at 30mph; 50km/litre at 50km/h for standard engine)

Hybrid-Electric and Fully-Electric Models

  • Battery-electric and extended-range series-hybrid (gasoline-electric) models in development (diesel-electric has excessive size/weight but lightweight alternatives in research)
  • Same size, weight, main components as gasoline models
  • Up to 1 hour silent running on full-electric (approx. 30 miles at 30mph; 50km at 50km/h)
  • Up to 4 hours continuous running on hybrid-electric (approx. 120 miles at 30mph; 200km at 50km/h)
  • Hybrid has indefinite recharging using onboard micro-generator

*Gasoline contravenes the single fuel concept but the lightest commercial diesel engines weigh more than this entire motorcycle; we’re researching diesel micro-generators for long-range hybrid-electric models and have gasoline-hybrid and full-electric in pipeline

New Zealand Army Testing

Pictured below is an initial trial by Sgt Doug Middlemiss, RNZALR Instructor, Burnham Driver Training Wing, NZ Army.

After these and other trial runs Sgt Middlemiss reported:

“Extremely easy to operate, transport, lift…low noise…small footprint…this bike opens up a wide range of terrain that no other motorcycle could cover.”

NZ Army Headquarters then ordered a formal evaluation of the SLM versus their current Kawasaki KLR250.

Their instructors gave up trying to follow us down a super-steep bank with a rock field at the bottom.  We stopped halfway down, turned and traversed.  Their heavy bikes couldn’t stop sliding down into the rocks and got stuck.

They then tested our bikes over the terrain shown below (we weren’t permitted to film that test).  Instructors, officers and soldiers of all experience levels, some who had never ridden a motorcycle, all had success, and none crashed.

The verdict:  These bikes fill capability gaps they didn’t know they had, as a kind of range extender for foot soldiers, for reconnaissance, special forces and relief operations.

fx bikes army testing burnham fence lift

fx bikes army testing burnham

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FX Defense Super Lightweight Military Motorcycle


Trials vs FX

A surprising (to me) number of people compare the FX Mountain Moto to trials motorcycles, probably because both are at the light end of performance-off-road motorcycles.

The most obvious difference is that trials motos don’t have seats…it’s stand-up riding all the way.  FX has the geometry and footpeg-seat-handlebar triangle of a full size enduro motorcycle.

But you might be surprised at the amount of difference between the claimed “dry weight” of bikes and their actual ready-to-ride weight…it can be 20-40 lb+ (10-20kg)!  (See this article on dry vs wet weights)

If you get 2 bathroom scales with a wheel on each (or a more accurate setup!) your typical ready-to-ride Gas Gas will be 165 lb, maybe more.  Nothing against the Gas Gas…for what its designed for, competition trials, you couldn’t get much better.

FX starts at 132 lb ready-to-ride, so 30 lb lighter than a ready-to-ride trials bike, which is a big difference in agility and portability.

But the main differences are in the geometry and layout, e.g.

Trials bikes have a very steep fork angle so they can be balanced on the front wheel.  This becomes unstable and twitchy at higher speeds.

FX has a raked out fork angle, similar to an enduro bike, so it is very stable on steep terrain and is very comfortable on faster singletrack.

Trials footpegs are positioned to the rear of the bike for easy balancing on the back wheel, which is fine when standing up but not for longer distance seated riding.

FX footpegs are central like an enduro, keeping both wheels firmly on the ground and comfortable for stand up or seated riding.

Trials fuel tanks are about 1 quart / 1 litre with much thirstier engines than the 100mpg+ FX, which has a 2 gallon / 7 litre fuel tank.

For these reasons, any trials-based bikes that have tried using small seats have had to change their layout and end up more like enduro bikes with trials tires, with ready-to-ride weights over 190 lb.

From our experience, riders who enjoy FX the most are riders of enduro bikes AND trials bikes AND mountain bikes.  If someone is a purist, only enjoying one type of 2-wheeler, they sometimes can’t adjust to the unique riding experience of FX, which really is a crossover of all these.

Another example of the differences between trials and FX: Look at the wheels on trials/enduro…a rear trials tire weighs 22lb or so, with the heavier rim to match…around double the FX wheel weight…this is spinning unsprung mass which makes a proportionately-major difference to handling.

FX Bikes Early Concept: UniCross

FX Bikes UniCross Concept

FX Bikes UniCross Concept

Back in the earliest days of FX, before we were even called FX, there was…UniCross!

This was our first serious visualization of the super-lightweight powered mountain bike we were about to build.

Our technology incubator neighbor and mountain biking buddy, Campbell McGrouther, was a 3D artist and animator who eventually went into production of major motion pictures…we were lucky!

Cam did this mockup for us which was so photorealistic quite a few people, including some engineers at Porsche, thought it was real until we told them otherwise.

It was a great tool to start testing rider feedback on the design.  (The first change we made was to get rid of the bicycle seat!)

FX Bikes Early Concept


Derbi DH 2.0 Concept

Derbi DH 2.0 Concept

In many ways the UniCross and FX-1 concept was like the Derbi DH 2.0 concept that came years later (although the Derbi model was much prettier than our Ugly Duckling!):

  • Both were single speed with centrifugal clutch
  • The Derbi 100cc 4-stroke
  • UniCross was 120cc 2-stroke (grunty!)
  • Both weighed around 40kg / 88lb
  • Both used mountain bike wheels, suspension and brakes
  • Both were never going to work in their current forms!

We could tell you all the reasons why these concepts were not realistic, and why FX has moved to its current designs, but we’d rather let companies like Derbi (part of Piaggio) and anyone else wanting to make super-light motos or powered mountain bikes learn the hard way 🙂