2000–2006 Yamaha YFM400FWNP Big Bear 400 Supplementary Service Manual (P/N LIT-11616-15–22)

• Covers the 2000–2006 Yamaha YFM400FWNP Big Bear 400 (5FUA build)

• Official Yamaha OEM publication package: base manual P/N LIT-11616-13-22 and supplement P/N LIT-11616-15-22, totaling over 420 pages

• Features 12 exploded-view diagrams and 18 circuit diagnostic charts

• Comprehensive ATV workshop guidelines

• Factory maintenance and troubleshooting

• Complete engine overhaul procedures

• Drivetrain service tolerances

• Exact chassis geometry setup

• Electrical system diagnostics

• Constant velocity joint inspection

• Differential gear assembly

• Mikuni BSR33 carburetor tuning

• Primary and secondary clutch

• Steering knuckle mechanism

• Front double wishbone suspension

• Recoil starter maintenance

• CDI magneto testing

Factory Documentation

When you are troubleshooting the 2001 Big Bear 400, having the exact factory specs on hand prevents costly reassembly errors and ensures your rebuilds meet strict OEM tolerances. This complete service PDF details the critical mechanical and electrical data specific to the YFM400FWNP and its base models. Inside, you will find refined specifications for engine parameters, chassis geometry, and electrical system diagnostics. Working on these machines always requires proper safety precautions and the right protective gear, especially when testing active electrical loads or lifting the ATV. The guide provides essential wiring schematics for the ignition, starting, lighting, signal, and 2WD/4WD selecting systems. It organizes the troubleshooting logic clearly, guiding technicians through terminal continuity tests, component resistance checks, and circuit voltage verifications. By utilizing this reference directly at your workbench, you can perfectly match component resistance values and avoid ordering incorrect electrical parts during a complex repair.

To help you skip expensive dealership labor rates, this documentation outlines essential step-by-step instructions for tasks like bleeding the hydraulic brake system, servicing the constant velocity joints, tuning the Mikuni carburetor, and executing a timing chain replacement. Relying on highly detailed cable routing diagrams, lubrication diagrams, starting circuit operation schematics, valve dimension views, and gear lash measurement charts ensures a straightforward path through any major repair.

Technical Data Preview

What kind of data is included? The specification section accurately documents the engine idle speed at 1,450 ~ 1,550 r/min and lists the intake vacuum at 33.3 kPa (250 mmHg, 10 inHg). If you are diagnosing ignition issues, the pickup coil resistance is explicitly specified at 459 ~ 561 ohms at 20 °C (68 °F). The manual also defines the front axle geometry, including a 13° kingpin angle and a 4° caster angle. Electrical system references cover details down to the bulb wattage for the dual 12 V 30 W/30 W headlight setup.

A notorious repair trap when rebuilding the drivetrain involves the differential gear lash adjustment. Attempting to swap shims without following the precise calculation protocol—such as reducing the right shim thickness by 0.1 mm for every 0.1 mm of left shim increase—will instantly cause severe ring gear binding. Relying on the 0.09–0.47 mm tolerance specified in this factory manual completely eliminates these costly mistakes during your next repair.

Please note that this 2001 supplement contains specialized data and is designed to be used alongside the included base YFM400FWNM/NMC service manual for complete procedure steps.