ENGINE -
Engine Performance
- Liquid-cooled 250cc four-stroke churns out stronger mid- to high-range power
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Selectable Fuel Maps
- Increasing the YZ250FX's ability to tackle a wide range of riding environments, the ECU has been optimized with two improved fuel injection maps—both of which can be loaded and tuned in the Yamaha Power Tuner app—accessible through a handlebar-mounted map switch for on-the-fly adjustments to changing riding conditions. Pre-loaded maps include one for fast, aggressive high-traction conditions and one with a smoother engine character for extreme, low-traction conditions.
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Rearward-slanted, reversed cylinder design.
- rearward slant moves a significant amount of rotating weight toward the centre of the chassis
- rearward-slanted cylinder centralizes mass for excellent handling and a light, agile feel
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"Reversed" engine design (FI system is front-mounted, exhaust exits from rear of cylinder).
- forward-mounted FI provides straight intake path into the cylinder and provides optimum fuel/ air filling and flow for excellent power
- front-mounted intake design keeps fuel cooler since engine heat has less effect on incoming fuel (cooler fuel is more dense and increases power)
- design also helps centralize mass for light, agile handling
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Electric start with auto decompression system (no kick starter). Unit can be re-started in any gear.
- 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
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Lightweight titanium valves and optimized valve springs.
- titanium valves reduce reciprocating weight and allow for a higher rpm limit before valve float
- titanium valves means a fast-revving engine with smooth power delivery
- 31 mm titanium intake valves and 25 mm titanium exhaust valves
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Automatic cam chain tensioner.
- reduces maintenance
- special cam chain "sliders" reduce internal friction losses
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Lightweight, short-skirt, forged aluminum piston.
- light flat-top piston features lateral ribs on both sides of the piston pin area
- single compression ring and specially designed oil control ring increases surface contact area for optimal sealing
- 2-ring design decreases sliding resistance, reduces weight and provides faster throttle response
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Lightweight piston pin features a diamond-like coating (DLC) to reduce friction.
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Piston oil cooler jet nozzle directs oil to the desired portion of the cylinder and underside of piston.
- reduces piston, cylinder and rod temperatures for excellent durability
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"Liner-less" lightweight aluminum cylinder with ceramic composite coating.
- ceramic coating sprayed directly on the aluminum block, eliminating the need for a liner and reducing weight
- excellent heat dissipation for consistent power delivery
- coating enhances the thin film of oil between cylinder and piston, reducing friction and increasing power
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Cylinder and crankcase "cutaways" allow air "trapped" under the piston to enter special chambers or cutaways.
- reduces horsepower-robbing "pumping losses"
- crankcase cutaways match cylinder cutaways for maximum efficiency
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Ball-bearing-style crankshaft.
- bronze thrust washers located between crank webs and rod
- heat-treated for strength and durability
- balance ratio of the crank is optimized for minimal vibration and good torque feeling
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Nickel-chromium-molybdenum connecting rod.
- excellent strength and durability
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Lightweight, gear-driven counter balancer shaft.
- reduces vibration for improved rider comfort and less rider fatigue
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6-speed transmission utilizes a 2-bar, floating shift guide system and a 14 mm shift shaft.
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Heavy-duty, multi-plate clutch features a quick access magnesium outer cover.
- low-friction bushing on actuation arm reduces lever pull effort
- clutch is designed for the rigours of cross-country
- outer cover provides fast and easy clutch access
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44mm Keihin throttle body fuel injection system.
- 10-hole injector
- maximizes fuel atomization for optimal 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 starting and excellent throttle response
- cold start knob also doubles as an idle adjuster
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Handlebar-mounted engine trouble and low fuel warning lights.
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Exclusive Power Tuner app.
- Groundbreaking technology brings the power of the GYTR Power Tuner to your iOS or Android device
- onboard wifi allows adjustment of air/fuel mixture and ignition timing maps based on track conditions
- record race log information and monitor a range of data such as maintenance and system diagnosis, engine run time and more
- CCU is adopted to accommodate new Power Tuner
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Forward-mounted air box features a washable, dual-stage, foam air filter.
- airbox cover features flush mounted quick release fasteners
- no tools required to access air filter
- washable foam filter reduces tune up costs
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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
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Easy access "cartridge-type" oil filter.
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Compact, lightweight, single-core, YZ250F-based dual radiators.
- outstanding cooling efficiency
- pre-wired for accessory cooling fan - fits on right side rad only
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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
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High-capacity AC magneto eliminates need for a battery.
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Wrap-around exhaust system to match head, cam and intake.
- exhaust exits from the rear of the engine and circles cylinder body
- wrap-around 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
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Lightweight, aluminum, re-packable muffler (aka silencer).
- sound output is 94 dB meeting AMA regulations
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Works-style, race-spec "barrel adjuster" for on-the-fly clutch lever free play adjustments.
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Heavy-duty plastic engine skid plate
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Excessive lean angle sensor
- Will shut down the engine if the bike lays on its side
- helps prevent costly engine damage
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CHASSIS/SUSPENSION -
Bilateral Aluminum Frame
- The highly developed aluminum bilateral beam frame taken from the class-leading YZ250F has been tuned for cross country performance and modified to match the more powerful engine.
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Modified Balancer Position
- Position of the balancer weight has been adjusted to reduce vibration in the low- to mid-rpm range for less rider fatigue and increased long-distance comfort.
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Lightweight, tapered aluminum swingarm.
- lightweight design reduces unsprung weight for excellent suspension performance
- excellent rear wheel traction and control
- large 25 mm rear axle
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Lightweight detachable rear sub frame.
- constructed of square-section, lightweight aluminum pipe with no bends
- allows easy access when servicing rear suspension components
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YZ250F-based, 48 mm, adjustable, inverted, Kayaba "SSS" cartridge fork offers 310 mm (12.2") of wheel travel.
- fork seal design features a scraper for better cleaning performance in muddy conditions
- valving and settings are optimized for cross-country racing
- front fork adjustments include: 20-way compression damping and 20-way rebound damping
- optional fork springs are available through Genuine Yamaha parts.
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Fork features a twin-chamber, "Speed Sensitive System" design
- damper unit is in a separate structure (completely separated air and oil chambers)
- helps prevent 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
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Fork also features a Transfer Control Valve (TCV).
- TCV enhances damping from mid to full stroke and improves bottoming characteristics
- TCV offers more precise control throughout the full suspension stroke
- TCV is located on the upside of the spring and its function is controlled by piston speed, not piston position, hence the term "Speed Sensitive System fork".
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Large wrap-around plastic fork protectors provide excellent lower fork tube protection.
- self-supporting design reduces friction for smoother fork operation.
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YZ250F-based, Monocross link rear suspension features a fully adjustable Kayaba piggyback shock with 318 mm (12.5") of wheel travel.
- valving and settings are optimized for cross-country racing
- shock features separate adjusters for high- and low-speed compression damping
- shock adjustments include: threaded spring preload, 20-way low-speed compression damping, 2 turns of high speed compression damping and 30-way rebound damping
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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 and improved rider comfort
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Large 270mm floating front "wave-style" disc and compact Nissin twin-piston caliper.
- wave disc design reduces weight and improves cooling
- high-friction brake pads
- excellent braking performance
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"Shorty-style" adjustable front brake lever can be adjusted to fit various hand sizes.
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245 mm rear disc brake uses a "wave-style" disc and single piston Nissin caliper and Nissin master cylinder.
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Rear caliper and lower portion of the disc are protected by heavy duty plastic protectors.
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Lightweight, plastic resin 8.2 litre fuel tank is located under the seat.
- reduces centre of gravity and centralizes mass for exceptional handling performance
- tank can be flipped on its back without disconnecting fuel line (easy servicing under the tank)
- compact in-tank electric fuel pump
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Handlebar-mounted engine trouble and low fuel warning lights
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Compact bodywork.
- minimizes weight and enhances the lightweight feel and look of the YZ250FX
- flat design, "minimal" bodywork allows for fast, easy rider movements and 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 and will not peel off or get damaged by pressure washing
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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
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Rugged, 21" (1.60 x 21) front and 18" (1.85 x 18) D.I.D. rear rims.
- excellent durability
- reduce unsprung weight for optimal suspension performance and handling
- 18" rear wheel improves puncture resistance (Vs. 19" designs)
- Dunlop AT81 tires
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