Yamaha YZ125R 2003 Owner's Manual

Pages 264

Year 2003

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Yamaha YZ125R 2003 Specification

The Yamaha YZ125R 2003 is a high-performance motocross motorcycle engineered for competitive racing and agile handling. This model is equipped with a liquid-cooled, 124cc, single-cylinder, two-stroke engine that delivers robust power and rapid throttle response. The engine features a reed valve induction system and a Keihin PWK38 carburetor, which ensures efficient fuel delivery and optimal combustion. The six-speed transmission allows riders to seamlessly navigate through various terrains with precision.

The lightweight chassis of the YZ125R 2003 is constructed from a blend of aluminum and steel, providing a perfect balance between strength and flexibility. The suspension system includes fully adjustable KYB inverted front forks with 300mm of travel and a monocross rear shock with 315mm of travel, offering superior handling and stability over rough tracks. The braking system is comprised of a 250mm front disc and a 245mm rear disc, ensuring reliable stopping power.

The YZ125R 2003 has a dry weight of approximately 85 kg (187 lbs), making it one of the lighter bikes in its class, which contributes to its exceptional agility and maneuverability. The fuel tank capacity is 8 liters, allowing for extended riding sessions without frequent refueling. The ergonomically designed seat and handlebars offer comfort and control, enhancing the rider's experience during intense races.

Overall, the Yamaha YZ125R 2003 combines advanced engineering with high-quality components to deliver a competitive edge in motocross racing. Its powerful engine, responsive handling, and lightweight design make it a preferred choice for both amateur and professional riders seeking performance and reliability on the track.

Yamaha YZ125R 2003 F.A.Q.

What type of oil should be used in the Yamaha YZ125R 2003 engine?

The Yamaha YZ125R 2003 requires a high-quality 2-stroke engine oil. A synthetic or semi-synthetic oil designed specifically for 2-stroke engines is recommended for optimal performance.

How often should I clean the air filter on my YZ125R 2003?

The air filter should be cleaned after every ride in dusty conditions, or at least every 3-5 rides in normal conditions. Regular cleaning ensures the engine receives clean air, enhancing performance and longevity.

What is the correct spark plug gap for the YZ125R 2003?

The correct spark plug gap for the Yamaha YZ125R 2003 is 0.7-0.8 mm (0.028-0.031 inches). It's important to check and adjust the gap for optimal engine performance.

How can I troubleshoot a hard starting issue on my YZ125R 2003?

First, check the spark plug for fouling and ensure proper gap. Next, inspect the fuel system for any blockages. Ensure the air filter is clean and the carburetor is properly adjusted. If the issue persists, a compression test may be necessary.

What is the recommended tire pressure for the Yamaha YZ125R 2003?

The recommended tire pressure for the Yamaha YZ125R 2003 is 12 psi for both the front and rear tires. Adjust the pressure based on terrain and rider preference.

How do I adjust the chain tension on my YZ125R 2003?

To adjust the chain tension, place the bike on a stand, loosen the rear axle nut, and then adjust the chain adjusters on either side of the swingarm to achieve the correct tension. The ideal slack is about 1.2 inches (30mm) at the midpoint of the chain.

What maintenance should be done after a race on the YZ125R 2003?

Post-race maintenance includes cleaning the bike thoroughly, checking and tightening all bolts, inspecting the tires for wear or damage, cleaning and re-oiling the air filter, checking the brake pads, and lubricating the chain.

How can I improve the suspension performance on my YZ125R 2003?

To improve suspension performance, adjust the fork and shock settings to match your weight and riding style. Consider upgrading to aftermarket suspension components or springs if necessary. Regular servicing by a professional can also enhance performance.

What are common signs of carburetor issues on the YZ125R 2003?

Common signs of carburetor issues include poor idling, backfiring, difficulty starting, and a noticeable decrease in performance. Regular cleaning and proper tuning of the carburetor can help prevent these issues.

How can I prevent overheating on my Yamaha YZ125R 2003?

To prevent overheating, ensure the radiator is clean and unobstructed, use a high-quality coolant, and avoid prolonged idling. Regularly inspect the cooling system for leaks or damage.