2021 Yamaha WR250F

RACE-READY PERFORMANCE

Compared to the former WR250F engine, the current design is more powerful at higher rpm and delivers stronger power right through the rev range, making it a serious podium contender out of the box.

Engine

• Latest-gen "reversed" liquid-cooled, 250 cc, DOHC, 4-valve (titanium), single-cylinder engine with fuel injection. The engine has been tuned specifically for XC/woods racing with a broad, easy-to-use powerband and excellent power characteristics throughout the rev range.
• 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
• "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
• 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
• 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
• Automatic cam chain tensioner.
  • reduces maintenance
  • special cam chain "sliders" reduce internal friction losses
• 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
• Lightweight piston pin features a diamond-like coating (DLC) to reduce friction.
• 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
• "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
• 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
• 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
• Nickel-chromium-molybdenum connecting rod.
  • excellent strength and durability
• Lightweight, gear-driven counter balancer shaft.
  • reduces vibration for improved rider comfort and less rider fatigue
• 6-speed transmission utilizes a 2-bar, floating shift guide system and a 14 mm shift shaft.
• 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
• 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
• Handlebar-mounted engine trouble and low fuel warning lights.
• Optional, GYTR competition ECU and GYTR Communication Control Unit (CCU) kit.
  • Allows tailoring of both fuel injection and ignition mapping when used with Yamaha's free, exclusive Power Tuner app
  • Monitor real-time data, track engine run time and run engine diagnostics
  • Accurately log race data for future reference
  • Share maps with friends and teammates
  • Closed-course competition use only. Not for trail use
• 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
• 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.
• High-capacity radiator.
  • large YZ250F-derived radiator features a cooling fan for consistent performance
  • outstanding cooling efficiency
• 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 eliminates need for a battery.
• 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
• Lightweight, aluminum, re-packable muffler (aka silencer).
  • sound output is 94 dB meeting AMA regulations
• Works-style, race-spec "barrel adjuster" for on-the-fly clutch lever free play adjustments.
• Heavy-duty plastic engine skid plate
• Excessive lean angle sensor
  • Will shut down the engine if the bike lays on its side
  • helps prevent costly engine damage