1974-1978 Yamaha RD125 / RD200 Service Manual (P/N 507-28197-81)

• Details the 1974–1978 Yamaha RD125 and RD200 lineups, covering the 125B/C, 200B/C, DX, and RX variants for the factory-spec 2-stroke parallel-twin engines.
• Official Yamaha publication 507-28197-81 (first edition, September 1974).
• Features 47 exploded-view diagrams, 16 mechanical schematics, and 12 technical specification tables.
• Serves as the original reference for the launch build, documenting specific engine, chassis, and electrical parameters for the 507 and 397 factory series.

Documentation Walkthrough

Factory documentation is built to keep shop time efficient. This manual organizes exact technical data for both 125cc and 200cc parallel-twin engines. It starts with proper serial number identification and moves straight into strict maintenance schedules. You will find the complete intervals for ignition timing, cable adjustments, and routine lubrication. The book breaks down the mechanical requirements for everything from top-end maintenance and carburetor synchronization to transmission servicing and tracing electrical faults. While these pages provide the exact original factory specifications, always verify current shop safety protocols and consider having a certified technician review the work before firing up the engine.

Technical Specification Highlights

Data tables are split out by model variant to prevent cross-referencing errors. The RD125B is documented at a 124 cc displacement, while the RD200B sits at 195 cc. Assembly figures are highly specific. For example, the cylinder head bolt torque requires a precise 86.8–130.2 in-lbs (1.0–1.5 m-kgs). Diagnostic baselines list the ignition coil primary resistance at 4.0 ohms at 20°C, with a standard idle speed of 1150–1250 rpm for both machines. Fluid capacities are also hard-coded into the tables, specifying 700–800 c.c. of transmission oil for the RD125 and 800–850 c.c. for the RD200.