For 2017, there have been a number of significant improvements to the class leading 250cc power plant. A new cylinder head, cams, connecting rod and revised transmission top the list. On the chassis side, we have increased the width of the frame spars in the swingarm pivot area, optimized the outer fork tubes and tweaked the suspension settings.

• New cylinder head with revised intake & exhaust port shapes
• Revised intake & exhaust camshafts & valve springs
• Revised intake tract & intake manifold
• New connecting rod design
• New crankcase heat treating process
• Revised 5-speed transmission, shift drum & gear shift lever
• Revised wrap around exhaust system header pipe
• Revised ECU
• Revised frame & engine mounts
• Revised front fork outer tubes & damping settings

• The design goals for the fuel injected YZ250F are a balance of easy cornering, lightweight & compact feeling thanks to excellent mass centralization. The fuel injected engine features a wide, controllable power band that sets the standard in the 250 class.
• Revised, "reversed" liquid-cooled, 250cc, DOHC, 4-valve (titanium), single with fuel injection. The engine has been tuned for excellent "ride ability & controllability" and delivers a broad, easy to use power band with excellent power characteristics throughout the rev range. 2017 model changes improve power delivery in both low to mid and mid to top end performance.
• 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 & a light 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 & provides optimum fuel/ air filling & 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 & increases power)
  • design also helps centralize mass for light, agile handling
• Revised, 4-valve cylinder head features a 13.5:1 compression ratio.
  • intake port has been raised 4 mm (Vs. '16) for improved flow
  • larger diameter intake valve seats improve flow
  • improved power delivery across the rev range (low, mid & top)
  • 4-valve design offers optimum flow & excellent power
• Shorter internal air box funnel & new intake manifold with larger cross section.
  • improved fuel - air flow for increased power
  • improved over-rev feeling
  • reduced horsepower losses in the mid to high rpm (reduced friction as fuel-air "charge"
  • travels thru the intake tract)

• Lightweight titanium valves & revised load optimized oval valve springs.
  • titanium valves reduce reciprocating weight & allow for a higher rpm limit before valve float begins
  • intake & exhaust valve spring rates have been increased to match the revised cams
  • titanium valves means a faster-revving engine with smooth power delivery
  • 31 mm titanium intake valves & 25 mm titanium exhaust valves
• Automatic cam chain tensioner.
  • reduces maintenance
  • special cam chain "sliders" reduce internal friction losses
• Revised, intake & exhaust camshafts.
  • revised intake & exhaust cam profiles (working angle & lift) for improved power & "control-ability"
  • hollow design reduces weight
• "liner-less" lightweight aluminum cylinder features a ceramic composite coating applied directly to the aluminum block.
  • ceramic coating sprayed directly on the aluminum block, eliminating the need for a heavy liner & reducing weight
  • excellent heat dissipation for consistent power delivery
  • coating enhances the thin film of oil between cylinder & piston, reducing friction & increasing power

• Cylinder "cutaways" allow air "trapped" under the piston to enter a special side chamber (cutaway).
  • reduces horsepower-robbing "pumping losses"
• Crankcase also utilizes special "cutaways"
  • reduces horsepower-robbing "pumping losses"
  • crankcase cutaways match cylinder cutaways for maximum efficiency
• New heating treating process for crankcases.
  • heating treating process increases crankcase strength by 5%
  • improved crankcase strength matches increased power output
• Lightweight, short-skirt, forged aluminum piston.
  • flat top piston with lateral ribs on both sides of the piston pin area for strength & durability
  • single compression ring & specially designed oil control ring increases the surface contact area for better sealing
  • 2-ring design decreases sliding resistance, reduces weight & provides faster throttle response

• Lightweight piston pin with diamond like coating (DLC) to reduce friction.
• Piston oil cooler jet nozzle directs oil to the desired portion of the cylinder & underside of piston.
  • reduces piston, cylinder & rod temperatures for excellent durability
• Ball bearing style crankshaft.
  • heat treated for strength & durability
  • balance ratio of the crank has been optimized to reduce vibration & improve torque feeling
• New nickel-chromium-molybdenum connecting rod.
  • excellent strength & durability
  • increased strength (Vs. '16) to maintain precise big end roundness during high rpm & high load use
  • balance ratio of the crank has been optimized to reduce vibration & improve torque feeling
  • molybdenum coated thrust washers on either side of the rod to reduce friction
• Lightweight gear driven counter balancer shaft.
  • reduces vibration for improved rider comfort & less rider fatigue
• Revised, 5-speed transmission.
  • 3^rd pinion gear & 2nd & 3rd drive gears are wider for better contact & engagement
  • revised 1^st, 2^nd & 3^rd gear engagement dog shape for optimized engagement
  • new, stronger heat treated gear shift lever
  • revised shift drum with optimized fork grooves for improved shift feel & engagement
  • utilizes a 2-bar, floating shift guide system & a 14 mm shift shaft
  • good durability in the event of a crash (14 mm shift shaft)
  • see spec page for gear ratios
• Heavy duty, multi-plate, clutch with quick access magnesium outer cover.
  • quick access, lightweight, magnesium outer cover provides fast & easy clutch access
  • light lever pull for reduced hand fatigue

• 44mm Keihin throttle body fuel injection system.
  • 10-hole injector
  • maximizes fuel atomization for more complete combustion & excellent power delivery
  • FI benefits include automatic adjustments to insure the optimum fuel - air ratio regardless of outside air temperature & altitude
  • other benefits include excellent starting & excellent throttle response
  • cold start knob also doubles as an idle adjuster
• Injector spray pattern, spray direction & distance to the intake valves have been optimized.
  • forward mounted straight intake tract maximizes benefits of the FI system & improves 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
  • washable foam filter reduces tune up costs
• Wet sump lubrication system.
  • reduces weight (no remote oil tank or oil lines)
  • eases maintenance (easier & faster oil changes)
  • oil volume is optimized to reduce oil related drag & weight

• Easy access "cartridge-type" oil filter.
• Compact, lightweight, single core, dual radiators provide 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
• Revised ECU with new ignition mapping & fuel mapping for improved power & over rev feeling.
• High capacity AC magneto eliminates need for a battery.

• Revised, wrap-around exhaust system to match head, cam & intake improvements.
  • header pipe diameters have been revised for a 12 to 16% flow improvement
  • exhaust exits from the rear of the engine & 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 CMRC & AMA regulations
• 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 kick it & go.
• Works-style race-spec "barrel adjuster" for on-the-fly clutch lever free play adjustments.

• Revised, compact "Bilateral Beam" aluminum frame.
  • revised frame with wider spars in the swingarm pivot area (up to 12 mm wider)
  • revised steel engine mounts (shape & thickness... front = 8 mm & rear = 6 mm) for improved handling
  • frame & engine designs centralize mass for exceptional handling & maneuverability
  • frame offers an optimum rigidity balance between strength, rigidity & tuned flex, plus excellent shock absorbing qualities
  • frame design offers excellent "rider - machine communication" (a.k.a. feedback)
  • key goal of this chassis design is faster & easier cornering ... one of the keys to winning races
• Lightweight, tapered aluminum swingarm.
  • lightweight design reduces unsprung weight for excellent suspension performance
  • excellent rear wheel traction & control
  • large 25 mm rear axle
• Lightweight detachable rear sub frame.
  • constructed of square-section, lightweight aluminum pipe with no bends
  • allows easy access when servicing rear suspension components

• Revised, 48mm, adjustable, inverted, Kayaba "SSS" cartridge fork offers 310mm (12.2") of wheel travel.
  • outer tubes have been revised to optimize the rigidity of the tubes & to match frame & engine changes for improved chassis "behavior" & stability in rough sections
  • front fork adjustments include: 20-way compression damping & 20-way rebound damping
  • inner tubes feature a special friction reducing coating for reduced stiction
  • 22 mm front axle
  • optional fork springs are available through Genuine Yamaha parts
• Fork features a twin-chamber, "Speed Sensitive System" design
  • damper unit is in a separate structure (completely separated air & oil chambers)
  • helps prevent aerated fork oil from entering the inner damper assembly & degrading its damping abilities
  • since the inner damper is pressurized; it also eliminates bubbles forming in the oil
• Fork 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

• 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
• Monocross link rear suspension with 315 mm (12.4") of wheel travel.
  • features a fully adjustable KYB piggyback shock
  • separate adjusters for high- and low-speed compression damping
  • shock is in-line with the center axis of the frame for excellent control
  • shock adjustments include: threaded spring preload, 20 -way low-speed compression damping, 2 turns of high speed compression damping & 30-way rebound damping
• Large 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)
  • high friction brake pads
  • excellent braking performance

• "Shorty style" adjustable front brake lever can be adjusted to fit various hand sizes.
• 245 mm rear disc brake uses a "wave-style" disc & single piston Nissin caliper & Nissin master cylinder.

• Rear caliper & lower portion of the wave style disc are protected by heavy duty plastic protectors.
• Lightweight, plastic resin 7.5 litre fuel tank is located under the seat.
  • reduces centre of gravity & 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

• Compact body work.
  • reduces weight & enhances the lightweight feel and look of the YZ250F
  • 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 & strength
  • reduces unsprung weight for optimal suspension performance & handling
  • front rim size is 1.60 x 21"; rear is 1.85 x 19"
  • rear hub features second bearing on sprocket side for increased rigidity & durability

• Convenient oil level sight glass
• Lightweight, extra wide foot pegs
• Folding shift lever tip
• Lightweight chain guide / support helps reduce chance of chain derailment & helps protect rear sprocket
• Heavy duty rubber swingarm protector (chain)
• Heavy duty DID 520 chain
• Clutch cable features integrated silicone grease & Teflon liner for smooth cable operation
• Easy access GYTR Power Tuner & Yamaha Diagnostic tool connectors