Yamaha YZ490S and YZ490 Motocross Machine Owner's Manual and Service (1985-1986)

Yamaha YZ490S and YZ490 Motocross Machine Owner's Manual and Service (1985-1986)

Master your vintage motocross machine with this definitive service and repair guide, specifically designed for the legendary Yamaha YZ490 series. This manual is an essential resource for owners and mechanics looking to maintain the peak performance of Yamaha’s powerhouse 500cc class racers from the mid-80s.

Covering the 1986 YZ490S and the 1985-1986 YZ490 models, this comprehensive document provides the technical depth required for everything from routine race-day prep to complete engine overhauls.

Models Covered

• YZ490S (1986)
• YZ490 (1985-1986)

Professional-Grade Technical Insights

This manual is packed with specific data to ensure your machine meets competition standards. It includes detailed sections on:

• Engine Precision: Full specifications for the 490cc engine, including piston clearance (0.080–0.085 mm) and cylinder bore limits (standard 87.00 mm).
• Advanced Suspension Tuning: In-depth coverage of the Monocross "De Carbon" system and the unique Brake Actuated Suspension System (B.A.S.S.), designed to eliminate rear wheel hop during aggressive braking.
• Carburetion & Induction: Precise settings for the Mikuni carburetor, including main jet (#460) and pilot jet (#40) standards, plus maintenance for the Yamaha Energy Induction System (Y.E.I.S.).
• Chassis & Braking: Step-by-step guides for the front disc brake system and rear drum maintenance, including wear limits and torque values like the 100 Nm rear axle specification.

Machine Identification & Serial Numbers

To ensure you are ordering the correct parts or identifying your vehicle for security, use the identification guides provided in the manual:

• Vehicle Identification Number (VIN): Located on the right side of the steering head pipe.
• Engine Serial Number: Stamped on the elevated part of the right rear section of the engine.
• Part Numbers: Includes specific reference codes such as the manual part number LIT-11626-05-11.

Mobile-Optimized Table of Contents

• General Information: Machine ID, control functions, and break-in procedures.
• Regular Maintenance: Detailed lubrication charts and interval schedules for every race.
• Engine Maintenance: Comprehensive repair steps for the reed valve, cylinder head, and transmission.
• Chassis Maintenance: Front fork settings, steering head adjustments, and swingarm service.
• Electrical System: Wiring diagrams and CDI magneto troubleshooting.
• Appendices: Tightening torques and general specifications.

Whether you are restoring a classic or keeping your racer track-ready, this manual provides the clarity and technical accuracy needed to protect your investment and dominate the dirt.