The Legendary Two-Stroke Motocrosser
The YAMAHA – YZ125 Bikes represent the pinnacle of two-stroke motocross engineering. In production since 1974, the YZ125 is the only remaining factory-supported 125cc two-stroke on the market . For 2025 and 2026, Yamaha has further refined this legendary platform to maintain its dominance in the highly competitive 125 class .
Most Powerful 125cc Engine Ever
At the heart of the YAMAHA – YZ125 Bikes lies a liquid-cooled, 124cc reed-valve-inducted two-stroke engine . For 2026, the intake system has been redesigned with an enlarged air filter housing and optimized carburetor settings, delivering more consistent throttle response and smoother corner exit power .
The engine features Yamaha’s famous YPVS (Yamaha Power Valve System), which broadens the powerband and provides exceptional low-end torque without sacrificing top-end over-rev .
Precision Carburetion
Unlike many modern bikes that have switched to fuel injection, the YZ125 retains a high-tech carburetor for optimal performance. The YAMAHA – YZ125 Bikes utilize a Keihin PWK38S carburetor with a solenoid-controlled powerjet . This system, combined with a Throttle Position Sensor (TPS) and 3D-map-controlled CDI, ensures explosive power out of the gate and crisp throttle response throughout the rev range .
Class-Leading KYB Suspension
The handling characteristics of the YAMAHA – YZ125 Bikes are widely considered the gold standard in the class. It features a KYB® Speed-Sensitive System (SSS) inverted fork, fully adjustable with 11.8 inches of travel . The rear is matched with a KYB fully adjustable shock providing 12.4 inches of travel . For 2025/2026 models, low-speed damping settings have been optimized, and tool-free compression adjusters have been added to the fork tops for quick track-side tuning .
Race-Ready Chassis and Geometry
The YAMAHA – YZ125 Bikes utilize an aluminum semi-double cradle frame designed for the perfect balance of rigidity and flex. This provides exceptional cornering performance and stability at high speeds . The bike’s ergonomics have been refined with a flat seat, narrow fuel tank, and slim radiator shrouds, allowing riders to move their body weight effortlessly for maximum control during braking, acceleration, and cornering . The sharp steering geometry features a 26° rake angle and 4.3 inches of trail .
Powerful Hydraulic Brakes
For stopping power, the YAMAHA – YZ125 Bikes are equipped with a 270mm front disc and 240mm rear disc with large-diameter pistons and rigid calipers . This setup provides exceptional braking performance and excellent feel, even under the heavy demands of motocross racing.
Smooth-Shifting 6-Speed Transmission
A close-ratio, constant-mesh 6-speed transmission allows riders to stay in the optimal powerband . Whether you are exiting a tight corner or charging down a long straight, the gearbox on the YAMAHA – YZ125 Bikes is designed to put the power to the ground efficiently.
2025 vs. 2026 Model Highlights
Who Is the YZ125 For?
The YAMAHA – YZ125 Bikes are perfect for:
- Youth racers moving up from 85cc classes.
- Lightweight adult riders looking for a nimble, agile race bike.
- Enthusiasts who love the thrill of a high-revving two-stroke.
- Riders seeking the lowest ownership costs with easy engine maintenance.
To protect your investment, read our Two-Stroke Maintenance Guide. For riding gear tips, follow our Motocross Safety Guide.
Pros:
- Liquid-cooled 125cc 2-Stroke with YPVS.
- KYB SSS fully adjustable suspension (front and rear).
- Aggressive, race-ready aluminum frame.
- 6-speed close-ratio transmission.
- Latest 2026 updates for smoother, more usable power.
- Lightweight agility (approx. 212 lbs wet) .
- Available 70th Anniversary Edition graphics .
Cons:
- Race bike ergonomics may be aggressive for casual trail riders.
- Requires pre-mix fuel (no oil injection).
- Peak power requires keeping the engine in high RPMs.
YAMAHA – YZ125 Bikes: Technical Specifications (2025/2026)
- Engine: 125cc Liquid-Cooled 2-Stroke w/ YPVS & Reed Valve
- Bore x Stroke: 54.0mm x 54.5mm
- Fuel Delivery: Hitachi Astemo® Keihin PWK38S
- Transmission: 6-Speed Constant Mesh
- Front Suspension: KYB® Inverted Fork, 11.8-in travel (Fully Adjustable)
- Rear Suspension: KYB® Monoshock, 12.4-in travel (Fully Adjustable)
- Front Brake: Hydraulic Disc, 270mm
- Rear Brake: Hydraulic Disc, 240mm
- Front Tire: 80/100-21 Bridgestone® Battlecross X20F
- Rear Tire: 100/90-19 Bridgestone® Battlecross X20
- Seat Height: 38.6 inches (980 mm)
- Ground Clearance: 14.4 inches
- Fuel Capacity: 1.8 gal (8 L)
- Wet Weight: 212 lbs (96 kg)
Why Choose a YZ125?
The YAMAHA – YZ125 Bikes represent the intersection of nostalgia and cutting-edge performance. While the market has shifted toward four-strokes, Yamaha remains committed to the 125 two-stroke, ensuring it gets continuous engineering updates .
The 2026 model year focuses on making the power more usable. Riders will find it easier to exit corners without the bike bogging down, thanks to optimized intake and ignition timing . The legendary KYB suspension remains the benchmark for handling and bump absorption, giving riders the confidence to push harder than ever before.
If you are looking for a race bike that is lightweight, inexpensive to rebuild, and incredibly fun to ride, the YAMAHA – YZ125 Bikes are the ultimate choice.
Browse our Collection of Motocross Bikes or read our Motocross Buying Guide to find your perfect match.
