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Lightweight, compact, liquid-cooled, 249cc, piston-reed-valve-inducted, 2-stroke.
- 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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The YZ250X offers serious two-stroke power in a super lightweight package. Yamaha modified the engine and changed the gear ratios in the 5-speed transmission to better suit cross country racing. The result is a good depth of power with an easy-to-use engine character.
Key Features
