1975-1980 Yamaha RD125 / RD125B / RD125DX Owner's Manual (P/N 507-28199-81)

• Official 86-page Yamaha Motor Co., Ltd. publication (P/N 507-28199-81), printed in Japan in February 1975.
• Covers the 1975–1980 Yamaha RD125, RD125B, and RD125DX models, including the specific hydraulic braking system variants found on the DX.
• Documents initial technical specifications and service intervals for the entire series build.
• Features 6 detailed flow charts dedicated to fuel, compression, and ignition system troubleshooting.

Manual Content Overview

This manual is the primary reference for anyone maintaining these classic two-stroke machines. Instead of generic overviews, it breaks down the exact requirements needed to keep the bike running smoothly. The documentation organizes vehicle information into four distinct sections: exterior identification, control functions, riding fundamentals, and periodic maintenance schedules. It details the routine inspections your Autolube oil tank, transmission, fuel delivery, and electrical circuits require. It also covers the minor adjustments you will inevitably perform in the workshop, such as setting cable tension, checking chain slack, and calibrating the brakes. Because working on vintage motorcycle systems carries inherent physical risks, always verify torque specifications and wear appropriate protective equipment before handling mechanical components.

Specification and Technical Data Highlights

The technical tables are where this documentation really delivers for bench work. You will find precise lubrication charts calling out the correct motor oil and grease for components like brake camshafts, wheel bearings, and drive chains. It leaves no room for guesswork. Cylinder head spark plug tightening torque is strictly set at 2.5–3.0 m-kgs, and transmission oil capacity is defined at exactly 750 ± 50 cc. Ignition timing is critical on these two-strokes. Accordingly, the contact breaker point gap is specified at 0.3–0.4 mm. You will also find proper fluid level definitions for the cooling system, alongside dedicated hydraulic routing and reservoir data for the RD125DX front brake.