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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Technical Safety Notice
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This official OEM document is intended for professional technicians and skilled operators. Performing service on mechanical equipment involves inherent risks. By purchasing, you acknowledge that RepairLoader provides original manufacturer data for informational purposes. Always prioritize safety: use correct tools, wear protective gear, and consult a certified professional if you are uncertain of any procedure.

Yamaha Models Covered & Key Technical Specifications

Models: Yamaha WR400F, Yamaha WR426F
Sub-models / Variants: WR400F(N), WR426F(N), USA version, Europe version, Canadian version, Australia version, New Zealand version, South Africa version
Build Years: 1998–2002
Serial Numbers: 5NG1, 5NG2, 5NG4, 5GS9
Technical Data:

  • Engine displacement: 426 cm3 (WR426F), 399 cm3 (WR400F)
  • Engine type: Liquid-cooled 4-stroke, DOHC, single cylinder, forward inclined
  • Bore and stroke: 95.0 x 60.1 mm (WR426F), 92.0 x 60.1 mm (WR400F)
  • Compression ratio: 12.5:1
  • Transmission type: Constant mesh, 5-speed
  • Idle speed: 1,700–1,900 r/min
  • Coolant capacity: 1.2 liters
  • Fuel tank capacity: 8.0 L (standard), 12 L (USA/CDN versions)
  • Spark plug gap: 0.7–0.8 mm
Technical Specifications
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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

Yamaha Manual Features & Content Preview

1998–2002 Yamaha WR400F and WR426F Service Manual

  • Covers 1998–2002 Yamaha WR400F and WR426F off-road competition motorcycles, including the WR400F(N) and WR426F(N) variants
  • Original OEM publication 5NG-28199-30
  • Contains detailed exploded-view diagrams, maintenance specification tables, torque-check charts, and wiring diagrams
  • Accessible from your device as soon as the order is placed
  • OCR text layer lets you jump to a torque spec by keyword
  • This 758-page manual provides the factory-authorized reference for the engine, chassis, electrical, and tuning adjustments required for competitive racing use

Technical Documentation Scope

The 1998–2002 Yamaha WR400F and WR426F workshop publication details every system, including engine top-end, transmission, electrical, and suspension. It is structured into seven distinct chapters covering general information, specifications, periodic maintenance, engine mechanical, chassis assemblies, electrical diagnostics, and performance tuning. The manual provides specialized service parameters, including valve clearances, piston-to-cylinder tolerances, and ignition timing data for all regional model codes.

Specification and Reference Data

Technical data is presented in comprehensive tables, such as the cylinder head warp limit of 0.05 mm and the intake valve clearance of 0.10–0.15 mm. Engine oil capacity is documented at 1.5 liters for periodic changes in the 1998–2002 Yamaha WR426F. The what an OEM service publication covers is essential for correct fastener management; for example, spark plug torque is set at 13 Nm. The 1998–2002 Yamaha WR426F clutch spring free length is specified at 48.4 mm. 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 758-page Yamaha OEM workshop manual covering the 1998–2002 Yamaha WR400F and WR426F, documenting engine, chassis, electrical, and fuel-injection specifications for the 5NG and 5GS-series builds.

Document Reference: 5NG-28199-30

Manual FAQ, Purchase & Download Details

Does this 758-page service manual cover both the 1998-2002 Yamaha WR400F and WR426F model variants? keyboard_arrow_down

Document includes technical specifications and maintenance data specifically for the 1998-2002 Yamaha WR400F(N) and WR426F(N) series motorcycles.

What information does the manual provide regarding engine specifications like bore and stroke dimensions? keyboard_arrow_down

Maintenance specifications chapters contain detailed technical data for the engine, including bore and stroke dimensions, compression ratios, and valve clearance reference values.

Are there reference tables for tightening torques included in this service manual? keyboard_arrow_down

Chapter 2 of this document features comprehensive tables that list general torque specifications and specific values for various components across the engine and chassis.

Does the document include diagrams to assist with identifying parts during a disassembly process? keyboard_arrow_down

Manual contains exploded diagrams at the start of each removal and disassembly section to help identify parts and clarify the order of operations.

Can I download this manual in a digital format for use on multiple devices? keyboard_arrow_down

Product is delivered as a PDF file, allowing for flexible access across compatible digital devices.

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