2000–2002 Yamaha WR400F(M) Factory Service Manual (P/N 5GS-28199-30, 5NG-28199-30)

• Three Yamaha Owner’s Service Manuals for the 2000 WR400F and 2001–2002 WR400F/WR426F, supplied as a 2,192-page PDF set with English, French, German, and Spanish text.
• Engine repair coverage runs from camshaft timing and valve-guide service to crankcase separation, crankshaft installation, and transmission, shift-cam, and shift-fork inspection.
• KEIHIN FCR-MX39 carburetor service covers disassembly, float and jet inspection, accelerator-pump components, and the air-cut valve—not just idle adjustment.
• Front and rear brake overhaul includes calipers, master cylinders, and bleeding. Front-fork procedures cover disassembly, seal and bushing replacement, and damper-rod inspection.
• Map-controlled CDI and TPS diagnosis includes no-spark troubleshooting, ignition-coil and magneto tests, throttle-position sensor replacement and adjustment, and lighting-system fault tracing.
• Race-tuning sections address jetting by operating symptoms, final-drive gearing, spring selection, and compression/rebound damping, with setting-parts tables and suspension troubleshooting charts.

Document Structure and Coverage

Each manual follows seven chapters. It starts with vehicle identification and control functions, then moves through specifications, regular inspection and adjustments, engine, chassis, electrical, and tuning.

2000 — WR400F(M): a 654-page PDF, Yamaha manual reference 5GS-28199-30, first edition November 1999.

2001 — WR426F(N)/WR400F(N): a 762-page PDF, reference 5NG-28199-30, first edition September 2000.

2002 — WR426F(P)/WR400F(P): a 776-page PDF, reference 5NG-28199-40, first edition August 2001.

The page counts include all four languages, covers, and other front/back matter; they are not counts of English-only technical pages.

The 2000 book covers the 5GS-series WR400F, including WR400FM for the US and WR400F(M) for Canada, Australia, New Zealand, and South Africa, alongside the European model. In the later books, WR400F coverage is for Europe and Australia, identified as 5GS9 for 2001 and 5GSA for 2002. The WR426F sections cover US, European, Canadian, Australian, New Zealand, and South African versions.

Specification Highlights and Engine Repair

The WR400F uses a 399 cc, liquid-cooled, four-stroke DOHC engine; the later manuals also cover the 426 cc WR426F. Both have dry-sump lubrication and a five-speed transmission.

Lubrication coverage reaches the frame oil strainer, oil-pump rotors, and oil-delivery checks. The Lubrication Diagrams trace the engine oil circuit, while the Cable Routing Diagram identifies hose, cable, and wiring placement. Maintenance tables supply fluid capacities, head-warp limits, piston and cylinder wear specifications, valve clearances, and component-specific fastener torques.

The Pad Selection Table supports valve-clearance adjustment. Separate WR400F and WR426F clutch sections in the later manuals distinguish friction-plate arrangements and the WR426F clutch damper spring. Cooling-system work includes radiator-cap and system pressure testing, plus water-pump shaft, bearing, and seal service.

Carburetor and Electrical Differences

The 2002 carburetor chapter includes accelerator-pump timing adjustment. TPS setup also changes across the set: the 2000 and 2001 procedures use resistance-based adjustment, while the 2002 procedure specifies output-voltage adjustment. Those are reasons to use the matching edition rather than transfer settings between years.

The Electrical Components and Wiring Diagram identifies circuit connections and wire colors. Diagnostic flowcharts work through ignition, TPS, and lighting faults, including pickup/source coils and the neutral switch. Jetting tables distinguish throttle-opening ranges and identify alternate jets and needles by part number.

Chassis Repair and Suspension Tuning

Steering-head bearing replacement and swingarm service extend to the relay arm, connecting rod, thrust bearings, bushings, and seals. Rear-shock procedures cover removal, inspection, spring replacement, and mounting-bearing service; they do not cover an internal rebuild of the nitrogen-charged damper.

The Suspension setting charts connect symptoms such as binding, bottoming, and poor traction with the relevant checks and adjustments. Optional fork and shock springs are identified by part number and identification marks.

Factory tool lists include the clutch holding tool YM-91042 / 90890-04086 and fork seal driver YM-01442 / 90890-01442. Assembly cautions explain that uneven cam-cap tightening can damage the head, caps, and camshafts. Dropping the fork damper rod into the inner tube can damage the valve inside.

Before working on engine or suspension components, cross-reference the applicable factory torque specifications and observe the manual’s workshop safety precautions, particularly those for the pressurized rear shock.