1998-2002 Yamaha WR400F / WR426F Service Manual (P/N 5NG-28199-30)

• Covers 1998–2002 Yamaha WR400F and WR426F competition off-road models, including the WR400F(N) and WR426F(N) variants.
• Official OEM publication (Reference: 5NG-28199-30).
• 758 pages of factory-authorized engine, chassis, and electrical reference data designed for competitive racing setups.

Complete Workshop Reference

When you have a top-end torn apart on the bench, generic overviews do not cut it. This factory publication gives you the exact blueprint for every system on your WR. The manual breaks down the entire motorcycle across seven dedicated chapters. You get direct access to specifications for engine mechanicals, transmission routing, electrical diagnostics, and suspension assemblies. Whether you are dialing in the ignition timing for specific regional model codes or verifying piston-to-cylinder tolerances, the exact factory parameters are right there. No guesswork. Just the hard numbers you need to get the bike out of the shop and back in the dirt.

Critical Specifications and Safety

The documentation goes deep into the technical details required for professional bench work. You will find comprehensive charts covering everything from the 0.10–0.15 mm intake valve clearance to the 0.05 mm cylinder head warp limit. Need to verify the clutch pack? The spring free length is clearly listed at 48.4 mm. Even routine maintenance is strictly documented, calling out the exact 1.5-liter engine oil capacity for periodic changes.

Please keep in mind that working on high-performance competition machines carries inherent risks. Always double-check your fastener management—like the 13 Nm spark plug torque specification—and ensure you are operating with the correct tools in a safe shop environment. The reference figures provided here highlight the depth of the manual, but qualified mechanics should always rely on the full OEM documentation as the authoritative source before starting any mechanical work.