1998-2002 Yamaha WR400F / WR426F Service Manual

Troubleshooting and service data for WR400F and WR426F motorcycles, includes timing chain diagnostics, clutch adjustments, carburetor specifications, and complete torque procedures with 758 pages of factory technical guidance.

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Document Details

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Document Number / Seller:
23500 / Paul Rodriguez
File Size:
22.19 MB
File Type:
PDF
Language:
English, French, German
Pages:
758
Printable:
Yes
Category:
Motorbike
Last updated / verified
Oct 24, 2025

Models Covered & Key Technical Specifications

Yamaha WR400F(N), WR426F(N) — 1998–2002

Manufacturer Compendium | WR Series Section.

  • Basic weight reaches 121.5 kg across the model lineup
  • Overall length measures 2,171 mm from end to end
  • Bore and stroke dimensions total 95.0 × 60.1 mm
  • Fuel tank capacity holds 8.0 L for extended range
  • Spark plug gap specification maintains 0.7–0.8 mm clearance
  • Idle speed operates within 1,700–1,900 r/min parameters

Professional Workshop Service Manual & Technical Specifications

OEM-Grade Training Technical Manual: Yamaha Dual-Displacement Dirt Bike Service Reference

Model-Portfolio: WR426FN (USA), WR426F (EUROPE), WR426F(N) (CDN/AUS/NZ/ZA), WR400F(N) | Engine-Type: Four-Stroke DOHC Liquid-Cooled | Asset-ID: YAM-WR-400-426-SVC-758P

Assessment-Element Baseline Calibration-Spec
Documentation Scope 758 pages, 83 chapters Multilingual (EN/FR/DE)
Engine Configuration 399cc/426cc DOHC Liquid-Cooled 4-Valve Per Cylinder
Transmission Type 5-Speed Manual Clutch Chain Final Drive
Suspension Systems Inverted telescopic forks / Monoshock rear Adjustable compression/rebound damping

This comprehensive service manual documents complete specifications, maintenance procedures, inspection protocols, engine service methodologies, chassis service procedures, electrical system diagnostics, and performance tuning guidance for dual-displacement off-road motorcycle platforms. The documentation encompasses general machine specifications, scheduled maintenance intervals with lubrication point mapping, regular inspection and adjustment procedures with detailed clearance specifications, complete engine disassembly and reassembly documentation, chassis component service and alignment procedures, electrical system wiring diagrams with diagnostic protocols, and tuning adjustments for varied riding conditions.

Engine systems documentation includes crankshaft assembly specifications, piston and ring service procedures, valve train component specifications, carburetor adjustment parameters, fuel system component identification, cooling system maintenance procedures, and ignition system timing specifications. Chassis systems documentation covers frame and suspension component service, brake system component specifications, steering system adjustment procedures, wheel and tire maintenance protocols, and cable routing diagrams with tension adjustment specifications.

Chapter Coverage Area Page Range
1 General Specifications 1-45
2 Maintenance Specifications & Intervals 46-98
3 Regular Inspection & Adjustment Procedures 99-167
4 Engine Service & Disassembly 168-312
5 Chassis Service & Alignment 313-445
6 Electrical Systems & Diagnostics 446-598
7 Tuning & Performance Adjustments 599-758

Torque specification documentation includes connecting rod mating surface contact specifications, cylinder head fastener specifications, and crankcase assembly specifications, enabling precise reassembly with dimensional accuracy verification protocols throughout service procedures.

FAQ

Specify the **applicable** oil capacity for periodic changes without filter replacement on the WR426F. keyboard_arrow_down

1.6 L (1.41 Imp qt, 1.69 US qt) is required for standard maintenance intervals on the WR426F motorcycle engine.

What is the **exact** spark plug gap specification for ignition system assembly? keyboard_arrow_down

0.7 ~ 0.8 mm (0.028 ~ 0.031 in) provides optimal combustion and engine performance across operating conditions.

Calculate the **specific** primary reduction ratio for the WR426F transmission system. keyboard_arrow_down

62/21 (2.952) establishes the gear ratio between the primary drive and transmission input shaft.

What values are **designated** for the coolant system operating pressure in normal conditions? keyboard_arrow_down

110 kPa (1.1 kg/cm2, 15.6 psi) is the radiator cap opening pressure for the WR426F cooling system.

Assess the **critical** bolt torque requirement for the clutch boss securing assembly. keyboard_arrow_down

75 N·m (7.5 m·kg, 54 ft·lb) is the specified torque per maintenance schedules documented in pages 644-758 of the service manual.

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Reviews (4)

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This manual has been a game-changer for my maintenance routine. Clear instructions and detailed diagrams make repairs easy. Highly recommended!
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Rated 4 out of 5 stars
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I had a smooth experience downloading the manual. The email response was prompt, and the support staff were very helpful!
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A comprehensive guide that covers everything from basic maintenance to advanced repairs. A must-have for any DIY enthusiast!