The 1985 Yamaha YZ125 is a highly regarded motocross motorcycle, celebrated for its potent liquid-cooled 2-stroke engine and agile handling. This model, with its chassis code 4SS and engine code 4SS, represented a significant step in 125cc motocross technology, featuring a 6-speed transmission, wet multiple-disc clutch, and advanced Monocross rear suspension. Known for strong mid-range power and responsive performance, it competed directly with other leading machines of its era. The YZ125 line boasts a rich heritage in off-road racing, with Yamaha consistently pushing innovation in the sport.

This comprehensive Factory Service Manual in English provides detailed guidance for the complete repair, maintenance, and diagnostics of the 1985 Yamaha YZ125. It covers all essential systems, including the engine, fuel, ignition, transmission, suspension, brakes, electrical components, and chassis. The manual includes step-by-step procedures, troubleshooting charts, detailed wiring diagrams, exploded views, and precise technical specifications. It is an indispensable resource for owners, mechanics, and technicians seeking to maintain the optimal performance and longevity of their YZ125.