1986 Yamaha YZ125S Service Manual

• Documents the 1986 Yamaha YZ125S with exact technical data for the 125cc liquid-cooled 2-stroke engine and MonoCross suspension.
• Official 100-page Yamaha publication P/N LIT-11626-05-13 (1st Edition, August 1985).
• Details structural layouts via exploded-view diagrams to simplify parts identification during a complex transmission repair.
• Highlights critical torque values and setup parameters essential for accurate race-season builds.

Component and System Documentation

Workshop efficiency relies on quick access to accurate specs. This manual outlines systems ranging from routine upkeep to complete teardowns. You will find exhaustive sections covering fluid specifications, machine identification, and intricate engine repair. Chassis servicing and appendixed tuning data are laid out clearly. To help visualize complex assemblies, the documentation pairs these descriptions with high-contrast diagrams. This ensures mechanics can verify component placement at a glance.

Specification Highlights

Tolerances matter on vintage motocross bikes. The reference table lists the cylinder head warpage limit at exactly 0.03 mm. For the power plant, piston clearance is tightly specified between 0.055 and 0.060 mm. Moving to the chassis, securing the drive sprocket requires a precise 60 Nm of torque. You also gain direct access to factory-mandated torque settings for steering stem nuts, cylinder holding nuts, and brake disc fasteners. Working on high-performance machinery inherently carries physical risks, so always cross-reference these reference figures with the complete factory documentation before applying torque to critical fasteners.