Description
Conquer Dirt
Cross country and enduro racing have been experiencing increased popularity and growth. Based on the legendary YZ250 two-stroke, the X model has been developed using all of Yamaha's extensive two-stroke knowledge to produce a high-level cross country performer. The YZ250X is a lightweight, compact machine that is both exciting to ride and affordable to own and maintain.
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Performance
The YZ250X is a super light weight package that offers serious two-stroke power. The engineers modified the cylinder head, adjusted the compression ratio, revised the exhaust port timing and changed the gear ratios in the 5-speed transmission to better suit cross country racing (vs. the base YZ250). The YZ250X engine offers a good depth of power with an easy-to-use engine character. |
The Extras
Cross-country-focused chassis features include softer suspension settings front and rear, an 18-inch rear wheel for more puncture resistance, an aluminum side stand and a fuel petcock that offers a reserve position for peace of mind (vs. YZ250).
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Features & Benefits
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Key Features
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The YZ250X is based on the YZ250 2-stroke with the following additional features that enhance its competitiveness for cross country racing / riding.
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"Re-tuned" engine Vs. YZ250 (head, ignition, porting & YPVS)
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Wider ratio transmission gears Vs. YZ250 (3rd gear & higher)
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Heavy duty clutch
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Expansion chamber shape
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Unique front & rear suspension settings
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18" rear wheel
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Aluminum side stand
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On-off-reserve fuel petcock
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ENGINE
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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")
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easy & economical to maintain, service & rebuild
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Key engine differences Vs YZ250.
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revised cylinder head volume Vs. YZ250 (slight increase in volume Vs. YZ250)
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7.9:1 compression ratio (slightly less than YZ250)
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revised YPVS power valve (actuation rpm & shape)
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revised exhaust port (main) size & timing
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wider 3rd, 4th & 5th gears ratios
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expansion chamber front diameter (reduced)
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Lightweight, flat top forged aluminum piston.
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excellent durability
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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.
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excellent heat dissipation
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reduced weight (no heavy iron liner)
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reduced friction
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extended cylinder life
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Lightweight, ball bearing style crank.
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lightweight design for fast throttle response
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friction reducing crank seals
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YPVS power valve system features a total of three slides (one main and two auxiliary slides).
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YPVS system varies the exhaust port height & timing based on engine rpm
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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).
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precise fuel - air mixing
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extra-crisp throttle response throughout the powerband
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Special-design, 4-petal, carbon fiber reeds.
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excellent throttle response & engine performance across the entire RPM range
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Smooth-shifting, wide ratio 5-speed transmission.
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ratios are matched to engine output for maximum performance
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optimal hook-up for outstanding acceleration & corner-exiting power
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transmission features "involute splines" for smooth, positive shifting even under power
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wider 3rd, 4th & 5th gears ratios (Vs. YZ250) ... see spec sheet
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Heavy-duty, multi-plate clutch.
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Clutch spring load is reduced for easier clutch lever pull Vs. YZ250 (less fatigue)
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quick-access, outer clutch cover allows for fast, easy clutch maintenance
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CD (capacitor discharge) ignition system.
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delivers a precise spark for fast, sure starts
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ensures optimal timing at all rpms for fast, strong response
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High capacity, washable, dual-stage, foam air filter.
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excellent filtering qualities
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reduces maintenance costs ... foam filter is re-useable
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Large-capacity, dual radiators feature 10-row cores.
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maximum cooling efficiency
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Lightweight exhaust system.
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computer designed expansion chamber provides maximum engine performance
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lightweight, aluminum silencer is re-buildable for optimum performance & reduced noise levels
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sound output is 94 dB
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Works-style clutch lever & race-spec "barrel adjuster."
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light, easy lever pull
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lever position (reach) can be set to rider's preference
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for on-the-fly clutch adjustments
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CHASSIS/SUSPENSION
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Lightweight, aluminum, semi-double-cradle frame.
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combines with compact engine to provide an awesome power to weight ratio
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obvious benefit of an aluminum frame is a significant weight reduction
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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
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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.
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constructed of square-section, lightweight aluminum
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detachable design allows easy access when servicing rear suspension components
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reduces costs in the event of a loop out
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Lightweight, tapered design aluminum swingarm.
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produced by "hydro forming", a forming method that uses high pressure water to form shapes
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excellent rear wheel traction & control
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lightweight design
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Cast aluminum upper and forged lower triple clamps.
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strong yet lightweight
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fast, agile handling
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Adjustable handlebar mounts.
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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").
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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
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the inner damper is pressurized, it also eliminates bubbles forming in the oil
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"Speed Sensitive" design means the damping force is controlled by piston speed, not position in the fork
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low friction fork seals provide reduced stiction for a smoother stroke
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spring & damping settings are optimized for cross country use
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fork adjustments include: 20-way compression damping & 20-way rebound damping
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optional fork springs are available through Genuine Yamaha parts
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Fork also features a Transfer Control Valve (TCV).
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TCV enhances damping from mid to full stroke & improves bottoming characteristics
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TCV offers more precise control throughout the full suspension stroke
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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.
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provide excellent protection from dirt, mud & stone chips
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"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.
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features separate adjusters for high- and low-speed compression damping
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adjustments include: spring preload, 20-way rebound damping, 20-way low-speed compression damping & 2 turns of high speed compression damping
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spring & damping settings are optimized for cross country use
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18 mm damper rod
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Kashima coating (friction reducer) is used in the shock body & sub tank to reduce friction & improve suspension performance
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piggyback shock utilizes a full rebound oil lock system for excellent suspension function & great ride quality
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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.
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"wave" style rotor (disc) reduces weight, improves cooling (more surface area) & improves styling
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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.
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integrated master cylinder (fluid reservoir is integrated into the top of the master cylinder)
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"wave" style rotor (disc) reduces weight, improves cooling (more surface area) & improves styling
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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.
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increases the contact area between the sprocket & chain rollers
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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.
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provide excellent durability
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reduces unsprung weight for optimal suspension performance & handling
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"Flat-design" seat features multi density foam.
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provides good initial softness / comfort and then increases the firmness as more pressure is applied
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"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.
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on - off - reserve fuel petcock
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reserve amount is approx. 2 litres
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Lightweight aluminum side stand.
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DETAILS
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Slim design, aggressive bodywork allows easy rider movements
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Lightweight YZ250F/450F based wide footpegs provide excellent grip & ground clearance
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Rugged chain guide helps prevent the chain from de-railing and also helps to protect the rear sprocket.
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Serrated rear brake lever and folding shift lever tip
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Stainless steel, inner clutch cable provides excellent strength, smooth action and long life
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Heavy-duty 520 "O" ring chain
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E10 friendly fuel system components
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