Contents

- GENERAL INFORMATION
  - LOCATION OF IMPORTANT LABELS
  - DESCRIPTION
  - CONSUMER INFORMATION
  - INCLUDED PARTS
  - IMPORTANT INFORMATION
  - CHECKING OF CONNECTION
  - SPECIAL TOOLS
  - CONTROL FUNCTIONS
  - STARTING AND BREAK-IN
  - TORQUE-CHECK POINTS
  - MAINTENANCE AFTER BREAK-IN
  - CLEANING AND STORAGE
- SPECIFICATIONS
  - GENERAL SPECIFICATIONS
  - MAINTENANCE SPECIFICATIONS
  - TIGHTENING TORQUES
  - CABLE ROUTING DIAGRAM
- REGULAR INSPECTION AND ADJUSTMENTS
  - MAINTENANCE INTERVALS
  - PRE-OPERATION INSPECTION AND MAINTENANCE
  - ENGINE
  - CHASSIS
  - ELECTRICAL
- ENGINE
  - SEAT, FUEL TANK AND SIDE COVERS
  - EXHAUST PIPE AND SILENCER
  - RADIATOR
  - CARBURETOR AND REED VALVE
  - CYLINDER HEAD, CYLINDER AND PISTON
  - CLUTCH
  - KICK SHAFT AND SHIFT SHAFT
  - YPVS GOVERNOR
  - WATER PUMP
  - CDI MAGNETO
  - ENGINE REMOVAL
  - CRANKCASE AND CRANKSHAFT
  - TRANSMISSION, SHIFT CAM AND SHIFT FORK
- CHASSIS
  - FRONT WHEEL AND REAR WHEEL
  - FRONT BRAKE AND REAR BRAKE
  - FRONT FORK
  - HANDLEBAR
  - STEERING
  - SWINGARM
  - REAR SHOCK ABSORBER
- ELECTRICAL
  - ELECTRICAL COMPONENTS AND WIRING DIAGRAM
  - IGNITION SYSTEM
- TUNING
  - ENGINE
  - CHASSIS

Yamaha YZ125J2 YZ125 2018 Owner's Manual

Pages 236

Year 2018

Language(s)

of 236

Yamaha YZ125J2 YZ125 2018 Specification

The Yamaha YZ125J2 YZ125 2018 represents a pinnacle in motocross engineering, designed for both competitive performance and durability. This two-stroke motocross bike is powered by a 124cc liquid-cooled engine, featuring Yamaha's renowned Power Valve System (YPVS) which optimizes power delivery across the RPM range. The engine is paired with a six-speed transmission, providing riders with the flexibility and control needed for various track conditions.

The frame of the YZ125J2 is a lightweight aluminum construction, contributing to the bike's agility and responsiveness. It incorporates a semi-double-cradle design that enhances rigidity while maintaining optimal weight distribution. The suspension system features a fully adjustable KYB Speed-Sensitive System fork in the front and a KYB shock with Kashima Coat on the rear, ensuring superior handling and comfort over rough terrain.

Braking is handled by a high-performance system with a 270mm front disc and a 245mm rear disc, offering exceptional stopping power and control. The bike is equipped with 21-inch front and 19-inch rear wheels, wrapped in Dunlop MX3S tires, known for their grip and durability on various track surfaces.

Ergonomics are carefully considered with a flat seat, tapered handlebars, and adjustable levers, providing riders with a comfortable and commanding riding position. The 2018 YZ125J2 also features a sleek, aggressive bodywork design with modern graphics, enhancing its aesthetic appeal.

Overall, the Yamaha YZ125J2 YZ125 2018 is engineered to deliver high performance, reliability, and rider-focused ergonomics, making it a top choice for motocross enthusiasts and competitive riders alike.

Yamaha YZ125J2 YZ125 2018 F.A.Q.

What is the recommended break-in procedure for the Yamaha YZ125J2 YZ125 2018?

The recommended break-in procedure involves gradually increasing the engine load over the first 10 hours of riding. Start with low RPMs and avoid full throttle. After the first hour, change the transmission oil and inspect the air filter. Gradually increase the engine load and RPMs over the next 9 hours.

How often should I replace the air filter on the Yamaha YZ125J2 YZ125 2018?

The air filter should be checked and cleaned after every ride in dusty conditions. In normal conditions, inspect the filter every 2-3 rides and replace it as necessary or every 10 hours of riding.

What type of fuel is recommended for the Yamaha YZ125J2 YZ125 2018?

Use high-octane (at least 91 octane) unleaded gasoline for optimal performance. Avoid ethanol blends greater than E10, as they may cause engine damage.

How can I adjust the suspension on the Yamaha YZ125J2 YZ125 2018 for better performance?

Adjust the suspension by tuning the compression and rebound damping settings on the front forks and rear shock. Refer to the owner’s manual for base settings and adjust according to your weight, riding style, and terrain.

What is the correct spark plug gap for the Yamaha YZ125J2 YZ125 2018?

The correct spark plug gap for the Yamaha YZ125J2 YZ125 2018 is 0.024-0.028 inches (0.6-0.7 mm). Use a feeler gauge to ensure the gap is within this range for optimal ignition performance.

How do I troubleshoot starting issues with the Yamaha YZ125J2 YZ125 2018?

If the bike is hard to start, check the spark plug for fouling, ensure the fuel is fresh, and inspect the air filter for clogs. Also, verify that the carburetor is clean and the fuel mixture is correct.

What regular maintenance tasks are recommended for the Yamaha YZ125J2 YZ125 2018?

Regular maintenance includes checking and cleaning the air filter, changing the transmission oil every 10 hours, lubricating the chain, inspecting brakes, and checking the tire pressure before each ride.

What are common signs that the piston and rings need replacing on the Yamaha YZ125J2 YZ125 2018?

Common signs include a drop in compression, excessive smoke from the exhaust, loss of power, and unusual engine noise. It's recommended to inspect and potentially replace the piston and rings every 30-40 hours of riding.

How can I improve the throttle response on the Yamaha YZ125J2 YZ125 2018?

To improve throttle response, ensure the carburetor is properly jetted and clean, check that the throttle cable is correctly adjusted, and maintain a clean air filter. Consider upgrading to a high-performance exhaust system for additional gains.

What type of transmission oil is suitable for the Yamaha YZ125J2 YZ125 2018?

Use a high-quality, 10W-40 or 10W-30 motorcycle transmission oil. Ensure it is specifically formulated for 2-stroke engines to provide optimal protection and performance.