Yamaha Big Bear 400, YFM400FWNM and YFM400FNMC ATV 2000–2001 Service Manual (P/N LIT-11616-13-22, LIT-11616-13-34)

• A 543-page PDF set — a 375-page service file made up of the 339-page base manual and 36-page supplement, plus a separate 168-page owner’s manual. Factory identifiers are LIT-11616-13-22 / 5FU-F8197-E0, LIT-11616-13-34 / 5GW-F8197-E0, and owner’s manual P/N LIT-11626-14-11.
• Exact service labels: the base manual covers YFM400FWNM/YFM400FWNMC, model codes 5FU1 except California and 5FU2 for California. The supplement is labeled YFM400NM/YFM400NMC, model codes 5GW1/5GW2, and Yamaha directs that it be used with the 5FU base manual.
• Engine repair runs from removal through full teardown, inspection, reassembly, and remounting. Coverage spans the cylinder head and valve train, timing system, piston and crankshaft, balancer and oil pump, recoil and electric starting parts, wet centrifugal clutches, shifter, and transmission.
• Drive-train repair covers the middle gear, front differential, constant-velocity joints, rear axle, final drive, and drive shaft. Factory procedures address bearing-retainer service, pinion and ring-gear shim selection, gear-lash measurement, differential operation checks, and U-joint assembly.
• Chassis procedures address front and rear wheels, the front disc-brake caliper and master cylinder, rear drum brake, hydraulic bleeding, steering shaft and tie rods, ball joints, front arms, shock absorbers, swingarm, toe-in, and suspension adjustment.
• Electrical and fuel-system diagnosis includes Mikuni BSR33 carburetor service and fuel-level adjustment, separate 5FU1/5FU2 carburetor and ignition data, and circuit-based testing for CDI ignition, electric starting, charging, lighting, indicator circuits, oil-temperature/fan control, and carburetor warming.
• The separate YFM40FWNN(C) owner’s manual covers controls, pre-operation checks, starting, shifting and reverse, break-in, parking and loading, scheduled maintenance, basic troubleshooting, cleaning and storage, specifications, and safety-focused riding guidance.

Yamaha Big Bear 400 Manual Structure

Yamaha divides the base service manual into nine factory sections: general information, specifications, periodic inspection and adjustment, engine overhaul, carburetion, drive train, chassis, electrical, and troubleshooting. Each major teardown opens with an exploded assembly view. The procedures then follow Yamaha’s removal, inspection, repair, assembly, and installation sequence.

The engine chapters provide full top- and bottom-end coverage for the 386 cc air-cooled SOHC single. They document the constant-mesh five-speed transmission with reverse, primary and secondary clutch service, crankcase separation, crankshaft and transmission installation, valve-seat and valve-guide inspection, cam and rocker service, timing setup, and final engine adjustment.

Periodic service material goes beyond an interval chart. It covers compression and ignition-timing checks, valve and clutch adjustment, oil-temperature warning-light testing, brake inspection and bleeding, final and differential gear-oil service, CV-boot inspection, steering checks, toe-in, battery inspection, fuse testing, and headlight service.

The base service manual is First Edition, June 1999. The supplement is First Edition, July 1999, and the owner’s manual is 1st Edition, April 2000. The 36-page 5GW supplement is not a stand-alone repair manual. Its scope is limited to changed YFM400NM/YFM400NMC information: general and chassis specifications, cable routing, periodic maintenance, engine removal and remounting, middle-gear inspection and assembly, shim selection, gear-lash checking, and front/rear wheel removal.

Specification, Tool, and Diagram Reference

Factory reference data covers component-specific torque tables, tightening sequences, lubrication points and lubricant types, fluid-capacity specifications, service clearances, inspection and wear limits, carburetor settings, gear backlash, and electrical test values. Separate 5FU1 and 5FU2 columns distinguish California and non-California carburetor calibration and ignition-advance data instead of treating both versions as identical.

The special-tool section gives Yamaha/YU/YM and 90890-series numbers for work that is difficult to perform correctly with improvised tools. Examples include crankcase separating tool YU-01135-A / 90890-01135, gear-lash measurement tool YM-01231 / 90890-01231, bearing-retainer wrench YM-04050 / 90890-04050, ball-joint remover/installer YM-01474 / 90890-01474, and electrical pocket tester YU-03112 / 90890-03112.

Reference graphics include the engine lubrication diagram, cable-routing views, exploded assembly drawings, the full YFM400FWN wiring diagram, and circuit diagrams for ignition, starting, charging, lighting, signal, cooling, and carburetor-warming systems. Troubleshooting charts trace hard-starting and performance faults, shaft-drive and shifting problems, clutch slip or drag, overheating, weak braking, suspension and handling faults, and lighting problems.

The manual flags two easy-to-miss drive-train repair traps: direct pressure on the middle driven-shaft end can damage its threads, and displaced U-joint needles can keep the yoke from seating correctly.

Included Owner’s Manual

The 168-page YFM40FWNN(C) owner’s manual is the operating and routine-maintenance companion. It explains controls and warning labels, the oil-temperature light, brake and shift controls, recoil starter, auxiliary DC jack, pre-ride checks, riding techniques, routine maintenance, wheel and battery service, troubleshooting, and storage. It does not replace the shop-level overhaul and electrical diagnosis chapters.

The service manual was written for Yamaha dealers and qualified mechanics and assumes practical repair knowledge. Experienced DIY owners can use the same factory data, but the ATV must be securely supported before engine, axle, brake, steering, or suspension work. Follow the manual’s precautions for fuel, battery service, brake fluid, compressed air, and rotating assemblies.