KEY FEATURES
The YZ250X is based on the YZ250 2-stroke with the following additional features that enhance its competitiveness for cross country racing / riding. - "Re-tuned" engine Vs. YZ250 (head, ignition, porting & YPVS)
- Wider ratio transmission gears Vs. YZ250 (3rd gear & higher)
- Heavy duty clutch
- Expansion chamber shape
- Unique front & rear suspension settings
- 18" rear wheel
- Aluminum side stand
- On-off-reserve fuel petcock
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ENGINE -
Lightweight, compact, liquid-cooled, 249cc, piston-reed-valve-inducted, 2-stroke.
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- super crisp, instant "right now" engine power (when in the "power band")
- easy & economical to maintain, service & rebuild
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Key engine differences Vs YZ250.
- revised cylinder head volume Vs. YZ250 (slight increase in volume Vs. YZ250)
- 7.9:1 compression ratio (slightly less than YZ250)
- revised YPVS power valve (actuation rpm & shape)
- revised exhaust port (main) size & timing
- wider 3rd, 4th & 5th gears ratios
- expansion chamber front diameter (reduced)
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Lightweight, flat top forged aluminum piston.
- excellent durability
- light weight means fast engine response
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"Liner-less", ceramic composite cylinder bore with ceramic coating sprayed directly on the aluminum block.
- excellent heat dissipation
- reduced weight (no heavy iron liner)
- reduced friction
- extended cylinder life
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Lightweight, ball bearing style crank.
- lightweight design for fast throttle response
- friction reducing crank seals
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YPVS power valve system features a total of three slides (one main and two auxiliary slides).
- YPVS system varies the exhaust port height & timing based on engine rpm
- provides the benefits of both solid, low rpm power delivery & strong top-end punch
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Keihin PWK38S carburetor with power jet & throttle position sensor (TPS).
- precise fuel - air mixing
- extra-crisp throttle response throughout the powerband
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Special-design, 4-petal, carbon fiber reeds.
- excellent throttle response & engine performance across the entire RPM range
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Smooth-shifting, wide ratio 5-speed transmission.
- ratios are matched to engine output for maximum performance
- optimal hook-up for outstanding acceleration & corner-exiting power
- transmission features "involute splines" for smooth, positive shifting even under power
- wider 3rd, 4th & 5th gears ratios (Vs. YZ250) ... see spec sheet
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Heavy-duty, multi-plate clutch.
- Clutch spring load is reduced for easier clutch lever pull Vs. YZ250 (less fatigue)
- quick-access, outer clutch cover allows for fast, easy clutch maintenance
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CD (capacitor discharge) ignition system.
- delivers a precise spark for fast, sure starts
- ensures optimal timing at all rpms for fast, strong response
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High capacity, washable, dual-stage, foam air filter.
- excellent filtering qualities
- reduces maintenance costs ... foam filter is re-useable
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Large-capacity, dual radiators feature 10-row cores.
- maximum cooling efficiency
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Lightweight exhaust system.
- computer designed expansion chamber provides maximum engine performance
- lightweight, aluminum silencer is re-buildable for optimum performance & reduced noise levels
- sound output is 94 dB
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Works-style clutch lever & race-spec "barrel adjuster."
- light, easy lever pull
- lever position (reach) can be set to rider's preference
- for on-the-fly clutch adjustments
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CHASSIS/SUSPENSION -
Lightweight, aluminum, semi-double-cradle frame.
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- combines with compact engine to provide an awesome power to weight ratio
- obvious benefit of an aluminum frame is a significant weight reduction
- Yamaha maintains the semi-double cradle design because it offers an excellent "rigidity balance" between lateral & torsional rigidity while offering controlled flex in the longitudinal plane
- result is a light aluminum frame, which provides excellent handling, good ride quality, excellent stability & responsive cornering performance
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Removable rear subframe.
- constructed of square-section, lightweight aluminum
- detachable design allows easy access when servicing rear suspension components
- reduces costs in the event of a loop out
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Lightweight, tapered design aluminum swingarm.
- produced by "hydro forming", a forming method that uses high pressure water to form shapes
- excellent rear wheel traction & control
- lightweight design
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Cast aluminum upper and forged lower triple clamps.
- strong yet lightweight
- fast, agile handling
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Adjustable handlebar mounts.
- allow handlebar to be moved 10mm rearward if desired
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"Speed Sensitive System" 48mm, adjustable, inverted, "twin chamber" KYB fork. Front wheel travel is 300 mm (11.8").
- twin chamber design means the damper unit is in a separate structure which prevents aerated fork oil from entering the inner damper assembly & degrading its damping abilities
- the inner damper is pressurized, it also eliminates bubbles forming in the oil
- "Speed Sensitive" design means the damping force is controlled by piston speed, not position in the fork
- low friction fork seals provide reduced stiction for a smoother stroke
- spring & damping settings are optimized for cross country use
- fork adjustments include: 20-way compression damping & 20-way rebound damping
- optional fork springs are available through Genuine Yamaha parts
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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".
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Large "wrap-around" plastic fork protectors.
- provide excellent protection from dirt, mud & stone chips
- "self-supporting" design reduces friction for smoother stroke
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Monocross link rear suspension features a fully adjustable, Kayaba, piggyback shock which provides 315 mm (12.4") of wheel travel.
- features separate adjusters for high- and low-speed compression damping
- adjustments include: spring preload, 20-way rebound damping, 20-way low-speed compression damping & 2 turns of high speed compression damping
- spring & damping settings are optimized for cross country use
- 18 mm damper rod
- Kashima coating (friction reducer) is used in the shock body & sub tank to reduce friction & improve suspension performance
- piggyback shock utilizes a full rebound oil lock system for excellent suspension function & great ride quality
- spring & damping settings are optimized for cross country use
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270 mm floating front "wave-style" disc brake with Nissin twin piston caliper.
- "wave" style rotor (disc) reduces weight, improves cooling (more surface area) & improves styling
- braking performance is excellent with great feel & control
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"Shorty" front brake lever is adjustable for various hand sizes.
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245 mm rear "wave-style" disc brake with single piston caliper.
- integrated master cylinder (fluid reservoir is integrated into the top of the master cylinder)
- "wave" style rotor (disc) reduces weight, improves cooling (more surface area) & improves styling
- strong stopping power with excellent feel & control
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Rugged, plastic rear caliper & lower rear disc protectors / guards.
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Lightweight, Sun Star rear sprocket.
- increases the contact area between the sprocket & chain rollers
- reduces the load on the chain & increases service life of chain & sprocket
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Heavy duty "O"- ring chain for excellent durability.
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Lightweight, D.I.D. 21" front and 18" rear rims & premium Dunlop tires.
- provide excellent durability
- reduces unsprung weight for optimal suspension performance & handling
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"Flat-design" seat features multi density foam.
- provides good initial softness / comfort and then increases the firmness as more pressure is applied
- "pebble" finish on the top and side surfaces provides excellent rider grip & durability
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Seat, handlebar & fuel tank ergonomics provide excellent freedom of movement for the rider.
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Large, 8 litre plastic resin fuel tank.
- on - off - reserve fuel petcock
- reserve amount is approx. 2 litres
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Lightweight aluminum side stand.
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DETAILS -
Bold New YZ Styling
- Along with the slimmer, more aggressive bodywork, a new front and rear fender design and new radiator shrouds all integrate with a bold new graphics scheme to highlight the YZ family pedigree. Premium Yamaha graphics are now embedded to provide excellent durability and scratch resistance.
- Slim design, aggressive bodywork allows easy rider movements
- Lightweight YZ250F/450F based wide footpegs provide excellent grip & ground clearance
- Rugged chain guide helps prevent the chain from de-railing and also helps to protect the rear sprocket.
- Serrated rear brake lever and folding shift lever tip
- Stainless steel, inner clutch cable provides excellent strength, smooth action and long life
- Heavy-duty 520 "O" ring chain
- E10 friendly fuel system components
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