1985-1986 Yamaha YZ490S / YZ490 Service Manual
Yamaha YZ490S and YZ490 technical guide detailing diagnostics, removal sequences, and maintenance for engine, chassis, and electrical systems. Includes P/N LIT-11626-05-11.
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Models Covered & Key Technical Specifications
Complete Overhaul Manual: Bike Yamaha YZ490S and YZ490 Motocross Machine Owner's Manual and Service (1985-1986) Knowledge-Base Yamaha YZ490S / YZ490 (LIT-11626-05-11) | Compendium Compendium.
- Published Gap Specs: 0.5 – 0.6 mm (0.020 – 0.024 in) establishes the standard spark plug gap Margin.
- Specific Assembly Gap: For optimal engine performance, 0.5-0.6 mm defines the spark plug gap clearance Margin.
- Integral Amperage Specs: 3100 ± 10% at 20°C (68°F) -- signifies the source coil resistance specification Protocol.
- Operational Feed Speed: The CDI unit requires 15 kV or more at 8000 r/min for proper ignition output Norms.
- Established DPI Rating: Primary coil resistance of 1.0Ω ± 15% at 20°C (68°F) corresponds to the ignition coil specification Bounds.
- Authorized Displacement Data: The engine displictes 490 cm³ (30 cu in) yielding the standard compression ratio Topology.
Professional Workshop Service Manual & Technical Specifications
Complete Overhaul Manual: Bike Yamaha YZ490S and YZ490 Motocross Machine Owner's Manual and Service (1985-1986) Knowledge-Base
Reference-Category: YZ490S / YZ490 (1985-1986) // Reference-Category: Bike / Motocross Logic // Year-Coverage: 1985-1986.
| Specifications | Service-Nexus | Operational-Logic | Architecture |
|---|---|---|---|
| Engine Type | Air-cooled 2-stroke | Induction | |
| Displacement | 487 cm³ | Standard | |
| Bore x Stroke | 87 x 83 mm | Measurement | |
| Compression Ratio | 6.9 : 1 | Calculation | |
| Fuel | Premium | Octane |
Comprehensively establishing the operational logic and repair procedures for the Yamaha YZ490S and YZ490 motocross machines. This document provides in-depth guidance for various systems and components.
Hydraulic schematics are included for the brake system, detailing caliper and master cylinder components.
Steering component information is provided for the headset bearings, ensuring smooth control.
Inspection guidelines are provided for wear and tear on the drive chain and sprockets.
Alignment specifications are included for the rear wheel, crucial for stable handling.
Reference data is included for electrical system troubleshooting, covering CDI unit and ignition coil resistance.
The documentation is partitioned into sections covering General Information, Regular Maintenance and Adjustment, Engine Maintenance and Repair, Chassis Maintenance and Repair, Electrical Systems, and Appendices. Each section offers detailed procedures and specifications.
This manual documents torque specifications for critical components like the crankcase and clutch nut to ensure proper oscillation integrity.
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