For 2019, the reworked YZ450FX adopts all of the latest upgrades found on the YZ450F motocrosser, including the advanced frame, suspension, engine and electronics-including Yamaha's exclusive Power Tuner smartphone app-with changes designed specifically for the needs of cross-country/woods competitors.
A high-compression cylinder head, forged piston, aggressive cam profiles, cylinder geometry and much more work together to give YZ450FX riders the ideal power spread in challenging XC racing conditions.
The YZ450FX features a bilateral-beam aluminum frame focused on rigidity, durability and bump absorption, while class-leading KYB suspension with speed-sensitive damping provides exceptional handling, cornering feel and straight-line confidence.
Reversed, liquid-cooled, 449 cc, DOHC, 4-valve (titanium), fuel injected, single-cylinder engine.
- super convenient electric starting means faster re-starts and significantly reduced rider fatigue
- compact electric starter powered by a lightweight lithium ion battery
- Kick starter removed
- New, high-torque-type starter motor adopted for 2019
"Reversed" engine design (FI system is front mounted, exhaust exits from rear of cylinder).
- FI throttle body and air box are front-mounted, providing a straight intake path
- straight shot intake path provides optimum fuel / air / exhaust flow for excellent power
- front-mounted intake keeps fuel cooler since engine heat has less effect on incoming fuel (cooler fuel is more dense and increases power)
Rearward-slanted, reversed cylinder design centralizes mass.
- rearward slant moves a significant amount of rotating weight toward the centre of the chassis, centralizing mass for light, agile handling
Revised, 4-valve cylinder head features a new 12.8:1 compression ratio.
- compact combustion chamber provides optimum combustion speed while also reducing heat and power losses
- 4-valve design offers optimum flow for excellent power and torque
- 37 mm titanium intake valves and 30.5 mm titanium exhaust valves
Lightweight titanium valves use load-reduced oval valve springs.
- titanium reduces reciprocating weight and allows for a higher rpm limit (40% lighter than steel valves)
- reduced friction (load reduced) valve springs
High-lift intake and exhaust cams and valve springs.
- intake and exhaust cam profiles and cam timing optimized for increased power output
Lightweight titanium valves.
- titanium valves reduce weight and improve performance... titanium valves are 40-45% lighter than steel valves
- reduced valve weight improves valve train reliability and longevity
- reduced reciprocating weight allows for a higher rpm limit and better control of the valves
Automatic cam chain tensioner.
- reduces maintenance and mechanical engine noise
- special cam chain "sliders" reduce internal frictional losses
Lightweight, ceramic composite-plated "liner-less" aluminum cylinder.
- reduced weight (no sleeve or heavy liner); plating is sprayed directly on the aluminum block
- ceramic coating ensures faster, more uniform heat dissipation
- ceramic coating enhances the thin film of oil between the cylinder and piston, reducing friction and increasing power
Cylinder is offset relative to the crankshaft (to exhaust side).
- reduces frictional losses between piston and cylinder wall during the power stroke
Cylinder "cutaways" allow air "trapped" under the piston to enter a side chamber (or cutaway)
- reduces horsepower-robbing "pumping losses"
Crankcase also utilizes special cutaways.
- reduces horsepower-robbing "pumping losses"
- crankcase cutaways match cylinder cutaways for maximum efficiency
Lightweight, short-skirt, forged aluminum piston and piston pin.
- lightweight design means faster throttle response and reduced mechanical vibration for excellent durability
- DLC (diamond-like coating) on piston pin and special coating on piston skirt reduces frictional losses
Piston oil cooler jet nozzle directs oil to the cylinder, rod and underside of piston.
- reduces piston, cylinder and rod temperatures for excellent durability
Carburized connecting rod for excellent durability.
- carburization is a type of heat treating that adds strength and hardness
Lightweight gear driven balancer shaft.
- reduces vibration for improved rider comfort and reduces rider fatigue
Updated clutch with quick-access magnesium outer cover and on-the-fly barrel adjuster.
- quick-access outer cover provides fast and easy clutch access
- light lever pull for reduced hand fatigue during a long moto
- combination of friction plates changed
- pressure plate redesigned for improved clutch feel
- clutch lever load reduced
- works-style, race-spec barrel adjuster for on-the-fly clutch lever free play adjustments.
5-speed transmission with 2-bar, floating shift guide system and 14 mm shift shaft.
- gears are wide to match engine power
- floating shift guide system provides smooth, positive shifts
- 14 mm shift shaft provides good durability in the event of a crash
Lightweight, 44 mm Mikuni throttle body fuel injection system.
- 12-hole injector maximizes fuel atomization for more complete combustion and excellent power delivery
- FI benefits include automatic adjustments to insure the optimum fuel ? air ratio regardless of outside air temperature and altitude
- other benefits include excellent throttle response and starting
- cold start knob (FID) doubles as an idle adjuster
New Smartphone-based, wireless, Power Tuner app.
- super convenient, smartphone based Power Tuner
- no "hard" link required between the unit and smartphone... wireless signal via Wi-Fi
- app is free and will work with either iOS or Android platforms
- receiving communication control unit (CCU) is located under left side cover of bike
- adjustment range includes 16 settings for both fuel injection duration and ignition timing
- real-time machine monitoring function (engine rpm, throttle angle, battery voltage, coolant temp, intake air temp, outside air pressure, etc.)
- new maintenance function allows user to track hours of use for scheduled maintenance
- race log function is available to record and save settings from various tracks
- tuning maps and race logs can be shared
New engine map selector with handlebar switch.
- Two maps are initially set for standard and low speed
- Maps can be modified using the Power Tuner app
Forward mounted air box features a washable, dual-stage, foam air filter.
- No tools required to access air filter
- new airbox cover with single, quick-release fastener
- revised, washable dual-stage air filter
Wet sump lubrication system.
- reduces weight (no remote oil tank or oil lines)
- eases maintenance (easier and faster oil changes)
- oil volume is optimized to reduce oil related drag and weight
Easy-access "cartridge-type" oil filter for fast, easy oil changes.
- single-core, dual radiators provide outstanding cooling efficiency
Updated radiator with increased core size.
- Core size increased by 12 cm2
Maintenance-free transistor controlled ignition (TCI).
- produces a strong spark for fast starts
- provides precise ignition timing / mapping for optimum engine performance at any rpm
Lightweight, wrap-around exhaust system.
- muffler derived directly from YZ450F
- sound output is 94 dB, meeting MRC and AMA regulations
- new rubber muffler-mounting system reduces vibration and improves durability
Launch Control System (LCS).
- provides smoother, quicker starts with less wheel spin and front wheel lift
- allows rider to concentrate on clutch control, body position and machine
- system functions in 1st and 2nd gears only and is disabled when the bike is shifted into 3rd
- centralizes mass by moving weight closer to the centre of the chassis
- ECU controls the system and adjusts engine rpm to limit wheel spin and wheelies
- activation button is on the LHS handlebar and features a LED indicator light
Special "G" sensor system.
- shuts down fuel injection system if bike lies on its side for more than 10 seconds
- helps prevent costly engine damage
- no special procedure to re-start the bike... just hit the electric start button and go!