ENGINE

• • YZ450F based, “reversed” liquid-cooled, 450cc, DOHC, 4-valve (titanium), 4-stroke, single with fuel injection and electric starting. The engine has been tuned for excellent “ride-ability & controllability” delivering a broad, easy to use power band with excellent power characteristics.
  • Rearward slanted, reversed cylinder design.
    • rearward slant moves a significant amount of rotating weight toward the centre of the chassis
    • rearward slanted design centralizes mass for light, agile handling
  • “Reversed” engine design (FI system is front mounted, exhaust exits from rear of cylinder).
    • FI throttle body & air box are front mounted, providing a straight intake path
    • straight intake path into the cylinder provides optimum fuel/ air flow for excellent power
    • front mounted intake keeps fuel cooler since engine heat has less effect on incoming fuel (cooler fuel is more dense & increases power)
    • design centralizes mass for light, agile handling
  • Electric start with auto decompression system. Unit can be re-started in any gear.

Note: kick starter is available as an accessory (P/N = B91-15602-00-00).

• • there is no main ignition switch on this model
  • electric start button (RHS handlebar) activates the entire electrical system
  • kill switch (LHS handlebar) if held for a few seconds shuts down entire electrical system
  • removal of kick starter & related gears etc. reduces weight
• Compact 4-valve cylinder head features a 12.5:1 compression ratio.
  • titanium 37 mm intake valves & titanium 30.5 mm exhaust valves
  • 4-valve design offers optimum flow for excellent power & torque
  • compact combustion chamber design
• Lightweight titanium valves use load-reduced oval valve springs.
  • titanium reduces reciprocating weight & allows for a higher rpm limit (40% lighter than steel valves)
  • reduced friction (load reduced) valve springs
• Automatic cam chain tensioner.
  • reduces maintenance & mechanical engine noise
  • special cam chain “sliders” reduce internal frictional losses
• Lightweight hollow intake & exhaust camshafts.
  • provide a broad power band well suited to cross country type racing / riding
• Lightweight, “liner-less” ceramic composite plated aluminum cylinder.
  • reduced weight… no sleeve or heavy liner… plating is sprayed directly on the aluminum block
  • ceramic coating insures faster, more uniform heat dissipation
  • coating enhances the thin film of oil between the cylinder & piston, reducing friction & increasing power
• Cylinder is “offset” relative to the crankshaft (to exhaust side) reducing frictional losses between piston & cylinder wall during the power stroke.
• Cylinder “cutaways” allow air “trapped” under the piston to enter a side chamber (or cutaway) to reduce horsepower-robbing “pumping losses.”
• The crankcase also utilizes cutaways to reduce “pumping losses”. The crankcase cutaways match the cutaways in the cylinder for maximum efficiency.
• Lightweight, short-skirt, forged aluminum piston.
  • lightweight design means faster throttle response
  • reduced mechanical vibration for excellent durability
  • special coating on piston skirt reduces friction
• Piston oil cooler jet nozzle directs oil to the desired portion of the cylinder, rod & underside of piston.
  • reduces piston, cylinder & rod temperatures for excellent durability
• YZ450F inspired crankshaft & connecting rod features a carburizing process for excellent durability.
• Lightweight gear driven counter balancer shaft.
  • reduces vibration for improved rider comfort & reduces rider fatigue
• 5-speed, wide ratio transmission utilizes a 2-bar, floating shift guide system & a 14 mm shift shaft.
  • smooth, positive shifts
  • good durability in the event of a crash (14 mm shift shaft)
  • optimized ratios for good performance in difficult sections & solid top end speed for fast sections
  • see spec page for gear ratios
• Heavy duty, multi-plate, clutch with quick access magnesium outer cover.
  • clutch is designed for the rigours of cross country / enduro riding
  • light lever pull for reduced hand fatigue during long rides / races
  • quick access outer cover provides fast & easy clutch access
• 44mm Keihin throttle body fuel injection system.
  • 12-hole injector
  • maximizes fuel atomization for more complete combustion & excellent power delivery
  • FI settings are specific to cross country type riding
  • FI benefits include optimum fuel – air ratio regardless of outside air temperature & altitude
  • other benefits include excellent starting & throttle response
  • cold start knob also doubles as an idle adjuster
• The injector spray pattern, spray direction and the distance to the intake valves have been optimized. Forward mounted straight intake tract helps to maximize the benefits of the FI system & overall power output.
• Optional, compact, hand held “GYTR Power Tuner” allows tailoring of both fuel injection duration & ignition mapping.
  • 9- different setting points can be accessed for both fuel duration & ignition maps
  • maps can be stored & shared with other Power Tuners if desired
  • easy access GYTR Power Tuner connector port
• Forward mounted air box features a washable, dual-stage, foam air filter.
  • No tools required to access air filter
• Wet sump lubrication system.
  • reduces weight (no remote oil tank or oil lines)
  • eases maintenance (easier & faster oil changes)
• Easy access “cartridge-type” oil filter.
• Lightweight, YZ450F based, single core, dual rads.
  • pre-wired for accessory electric cooling fan (fits on right side rad only)
  • fan kit is available as a Yamaha Genuine accessory
• Maintenance-free transistor controlled ignition (TCI).
  • produces a strong spark for fast starts
  • provides precise ignition timing / mapping for optimum engine performance at all rpms
• High capacity AC magneto to power the FI system.
• Lightweight, wrap-around exhaust system
  • exits from the rear of the engine & circles cylinder body
  • design ensures the optimum tuned header length
  • maximizes exhaust “pulse effect” for excellent power delivery
  • centralizes mass by moving weight closer to the centre of the chassis
• Lightweight, aluminum, re-packable muffler (aka silencer).
  • YZ450F design with minor modifications… sound output is 94 dB
• Excessive lean angle sensor
  • Will shut down the engine if the bike lays on its side
  • helps prevent costly engine damage
  • no special procedure to re-start the bike… just kick it and go

CHASSIS/SUSPENSION

• YZ450F based, compact, lightweight “Bilateral Beam” aluminum frame.
  • centralizes mass for exceptional handling & manoeuvrability
  • frame offers an optimum rigidity balance between strength, rigidity & tuned flex, plus excellent shock absorbing qualities
• Lightweight, tapered aluminum swingarm.
  • lightweight design reduces unsprung weight for optimum suspension performance
  • excellent rear wheel traction & control
• Lightweight detachable rear sub frame.
  • constructed of square-section, lightweight aluminum pipe with no bends
  • allows easy access when servicing rear suspension components
  • reduces cost in the event of a loop-out
• YZ450F based, 48mm, adjustable, inverted, Kayaba “SSS” cartridge fork with 310mm (12.2″) of wheel travel.
  • valving & settings are designed for cross country racing
  • front fork adjustments include: 20-way compression damping & 20-way rebound damping
  • optional fork springs are available through Genuine Yamaha parts
• Fork features a twin-chamber, “Speed Sensitive System” design meaning the damper unit is in a separate structure (completely separated air & oil chambers) which prevents aerated fork oil from entering the inner damper assembly and degrading its damping abilities. Since the inner damper is pressurized, it also eliminates bubbles forming in the oil.
• Fork also features a Transfer Control Valve (TCV).
  • TCV enhances damping from mid to full stroke & improves bottoming characteristics
  • TCV offers more precise control throughout the full suspension stroke
  • TCV is located on the upside of the spring & its function is controlled by piston speed, not piston position, hence the term “Speed Sensitive System fork”.
• Large “wrap-around” plastic fork protectors provide excellent lower fork tube protection.
  • “self-supporting” design reduces friction for smoother fork operation
• YZ450F based, Monocross link rear suspension features a fully adjustable Kayaba piggyback shock providing 318 mm (12.5″) of wheel travel.
  • features separate adjusters for high- and low-speed compression damping
  • shock is in-line with the center axis of the frame for excellent control
  • shock valving & settings are tailored for cross country style racing
  • shock adjustments include: threaded spring preload, 20 -way low-speed compression damping, 2 turns of high speed compression damping & 30-way rebound damping
• 270mm floating front “wave-style” disc & compact Nissin twin piston caliper.
  • wave disc design reduces weight & improves cooling (wave design offer more surface area for better cooling)
• “Shorty style” adjustable front brake lever can be adjusted to fit various hand sizes.
• 245 mm rear disc brake features a “wave-style” disc & single piston Nissin caliper & master cylinder.
• Rear caliper & lower portion of the wave disc are protected by heavy duty plastic protectors.
• Lightweight, plastic resin 7.5 litre fuel tank with compact in-tank electric fuel pump.
  • reduces centre of gravity & centralizes mass for exceptional handling & a lightweight feeling
  • tank can be flipped on its back without disconnecting fuel line (easy servicing under the tank)
• Handlebar mounted engine trouble & low fuel warning lights
• Adjustable handlebar holders offer a total of 4 different handlebar positions with an adjustment range of 30mm.
  • suits wide variety of rider sizes
  • handlebar holders are rubber mounted for reduced vibration & improved rider comfort
• Compact body work.
  • reduces weight & enhances the lightweight feel and look of the YZ450FX
  • flat design, “minimal” bodywork allows for fast, easy rider movements & a natural riding position
  • minimal design aids in keeping the body looking good (less plastic to scratch or damage)
  • graphics are impregnated directly into the plastic rad shrouds & will not peel off or get damaged by pressure washing
• Flat seat design.
  • provides easy rider movements
  • features a “cap cover” to access the fuel cap
  • non-slip seat cover material resists clogging with dirt or mud
• Rugged Excel rims.
  • excellent durability
  • reduces unsprung weight for optimal suspension performance & handling
  • 18″ rear wheel improves puncture resistance (Vs. 19″ designs)
  • Front rim size is 1.60 x 21″, rear is 2.15 x 18″
  • Dunlop AT81 tires