2021 Yamaha YZ125X

 Level up your performance. Designed to be the perfect stepping stone toward a full size cross-country machine, the YZ125X is the pinnacle of lightweight, two-stroke performance on the race course.
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CHASSIS
An ultra-lightweight YZ125-spec frame features a carefully engineered combination of aluminum castings, forgings and extrusions for the perfect balance of rigidity and flex, with industry-leading fully adjustable, KYB speed sensitive spring-type suspension tested and tuned specifically for the needs of cross-country racers.

• YZ125 two-stroke engine with Yamaha Power Valve System (YPVS)
• Model-specific CDI unit
• Racing intake system
• Ultra-lightweight YZ125-spec frame
• Industry-leading, XC-specific adjustable KYB suspension
• Smooth shifting, 6-speed, close ratio transmission
• ''Gripper'' type seat and narrow fuel tank
• Adjustable, tapered aluminum handlebar
• 18-inch rear wheel and large rear sprocket

• Liquid-cooled, 125 cc, crankcase reed valve-inducted 2-stroke engine provides class leading power and acceleration.
  • super crisp, instant "right now" engine power (when in the powerband)
  • easy and economical to maintain, service and rebuild
• 7.5-degree cylinder angle & straight shot intake path through the combustion chamber.
  • maximum power output
• Ceramic composite cylinder bore is a "liner less" design with the ceramic coating sprayed directly on the aluminum block.
  • reduced weight (no heavy iron liner)
  • reduced friction
  • extended cylinder life
  • excellent heat dissipation for consistent power delivery
• Specially designed combustion chamber achieves a more complete burn at higher rpm.
  • class leading power
• Lightweight, flat top forged aluminum piston.
  • excellent durability
  • light weight means fast engine response
  • matches combustion chamber design for maximum power delivery
• Lightweight, ball bearing style crank.
  • lightweight design for fast throttle response
  • friction reducing crank seals
• Compact crankcases.
  • lightweight design
  • helps centralize mass
• Quick-access, magnesium outer (sub) clutch cover.
  • light weight design
  • speeds clutch access
• Close-ratio, 6-speed transmission uses optimized gear ratios.
  • 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
• Yamaha's patented YPVS system.
  • features a slide (guillotine) type power valve that provides the benefits of both solid, low-rpm power delivery combined with a strong top-end punch. This system varies the exhaust port height and timing based on engine rpm.
• Mikuni TMXx38 carburetor features a "D" slide design.
  • enhances overall power delivery
  • provides crisp throttle response at all rpms
• 6-petal, carbon fiber reed design.
  • for stronger high-rpm performance with greater over-rev capacity
• CD (capacitor discharge) ignition system.
  • delivers a precise spark for fast, sure starts
  • ensures optimal timing at all rpms for fast, strong response
• High capacity, washable, dual-stage, foam air filter.
  • excellent filtering qualities
  • reduces maintenance costs? foam filter is re-useable
• Large-capacity, dual radiators feature 10-row cores.
  • maximum cooling efficiency
• Lightweight exhaust system features a re-packable aluminum silencer which allows the rider / tuner to maintain the correct amount of back pressure for maximum engine performance while reducing noise.
• Works-style clutch lever & race-spec "barrel adjuster."
  • easy lever pull
  • for on-the-fly clutch adjustments

• Lightweight, aluminum, semi-double-cradle frame.
  • 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 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
• 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
• 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
• Cast aluminum upper and forged lower triple clamps.
  • strong yet lightweight
  • fast, agile handling
• Adjustable handlebar mounts.
  • allow handlebar to be moved 10mm rearward if desired
• "Speed Sensitive System" 48mm, adjustable, inverted, "twin chamber" KYB fork. Front wheel travel is 300mm (11.8").
  • fork adjustments include: 20-way compression damping & 20-way rebound damping
  • optional fork springs are available through Genuine Yamaha parts
  • low friction fork seals provide reduced stiction for a smoother stroke
  • 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
• 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"
• Large "wrap-around" plastic fork protectors.
  • provide excellent protection from dirt, mud & stone chips
  • "self-supporting" design reduces friction for smoother stroke
• Monocross link rear suspension features a fully adjustable, Kayaba, piggyback shock which provides 315mm (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
  • 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.
• 270 mm floating front 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
• "Shorty" front brake lever is adjustable for various hand sizes.
• 245mm rear 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
• Rugged, plastic rear caliper & lower rear disc protectors / guards.
• "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
• Lightweight, D.I.D. 21" front and 19" rear rims & premium Dunlop tires.
  • provide excellent durability
  • reduces unsprung weight for optimal suspension performance & handling
• "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
• Seat, handlebar & fuel tank ergonomics provide excellent freedom of movement for the rider.