1991 Yamaha YZ125B Owner's Service Manual

1991 Yamaha YZ125B Service Documentation

• Covers 1991 Yamaha YZ125B motorcycle, documenting the YZ125(B)/LC competition variant for technical review
• Official Yamaha publication P/N LIT-11626-07-55, 1st edition June 1990
• Contains 8 exploded-view assembly diagrams and 35 detailed torque specification tables
• File delivered as a direct download the moment payment clears
• Index-integrated PDF structure supports rapid system-level lookup
• Includes specialized tuning data for carburetor jets, reed valves, and suspension settings
• This 1991 first edition serves as the foundational reference for the YZ125B series launch build, documenting all factory-specified clearances and settings.

Manual Content and Coverage

The 1991 Yamaha YZ125B owner's service manual provides essential data for the 1991 Yamaha YZ125B competition motorcycle. This volume details general machine identification, including VIN and engine serial number prefix protocols, alongside extensive maintenance schedules for competition-ready performance. Major sections include complete teardown, inspection, and assembly procedures for the liquid-cooled two-stroke engine, transmission, YPVS governor, and chassis components.

Technical chapters cover front and rear suspension adjustment settings, brake system bleeding, transmission oil changes, and complete carburetor tuning. Information regarding motorcycle maintenance includes detailed cable routing diagrams and torque-check points for all critical frame fasteners.

Specification and Technical Data Preview

Engine components are documented with strict wear limits and clearance tolerances. Cylinder bore size is specified at 56.00–56.02 mm in the specification tables. Piston clearance is documented at 0.04–0.05 mm for the 124 cm³ powerplant. Magneto pickup coil resistance for the 1991 Yamaha YZ125B is listed at 4.5–5.5 ohms at 20°C.

Torque values for major assemblies are clearly cataloged for service use. Cylinder head nut torque is documented at 30 Nm in the general maintenance section. Coolant capacity for the 1991 Yamaha YZ125B cooling system is 0.9 liters total. Reference only — always consult a certified technician before performing service on this equipment. This 175-page Yamaha OEM service manual covers the 1991 Yamaha YZ125B, documenting engine, chassis, electrical, and carburetor specifications for the 3XJ-series build.