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.
Yamaha Models Covered & Key Technical Specifications
Models: Yamaha YZ490S, YZ490
Model Years: 1985–1986
Technical Data:
- Engine displacement: 490 cm³ (30 cu in)
- Spark plug gap: 0.5–0.6 mm (0.020–0.024 in)
- Spark plug torque: 20 Nm (14 ft-lb)
- Ignition timing: 2.0 ± 0.1 mm (0.080 ± 0.004 in) BTDC
- Fuel tank capacity: 10 liters (2.64 US gal)
- Transmission oil capacity (periodic change): 0.75 liters (0.79 US qt)
- Primary coil resistance: 1.0Ω ± 15% at 20°C (68°F)
- Source coil resistance: 3100Ω ± 10% at 20°C (68°F)
Yamaha Manual Features & Content Preview
1985–1986 Yamaha YZ490S and YZ490 Motocross Service Manual
- Built for owners and mechanics servicing the 1985–1986 Yamaha YZ490S and YZ490 competition machines
- Official Yamaha publication P/N LIT-11626-05-11, first edition dated August 1985
- Documents key technical data across 114 pages, including exploded-view mechanical assembly diagrams and critical torque specifications
- Stored against your account so you can retrieve it after a hard-drive loss
- Full-text search finds any part number in seconds
- This 1985–1986 Yamaha YZ490S official workshop manual contains the original technical specifications used for the YZ-series motocross development
Document Scope and Technical Walkthrough
The 1985–1986 Yamaha YZ490S owner's manual and service guide provides a detailed technical summary of maintenance for the 490 cc motocross engine. General information chapters define identification markers, fuel mixing ratios at 24:1, and long-term storage preparation. Engine maintenance sections document the disassembly and inspection of the reed valve system, Y.E.I.S. chamber, and clutch assembly, providing wear limits for friction plates and push rod runout.
Maintenance and Specification Highlights
Chassis data covers the Monocross suspension system, including rear shock gas pressure settings at 981 kPa (142 psi) and rebound damping adjustments. Steering head torque values are documented at 130 Nm (94 ft-lb) for the stem nut. Understanding parts documentation for vintage Yamaha allows for accurate maintenance of swingarm linkages and sprocket assemblies. Cylinder head torque is specified at 22 Nm (16 ft-lb) in a crisscross sequence. All service data shown here is for reference only — qualified technicians and the original OEM documentation remain the authoritative source for any hands-on work.
An official 114-page Yamaha OEM workshop manual covering the 1985–1986 YZ490S and YZ490, documenting engine, chassis, suspension, and electrical system specifications for the competition-focused two-stroke motocross build.
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