1997–1999 Yamaha Big Bear 350 4x4 Owner's Manual (P/N LIT-11616-10-58)

These two Yamaha factory publications cover the YFM350FWB from two sides: dealer-level repair and owner-level operation. The service volume is titled YFM350FWBJ and lists model codes 4WU1 for the U.S. and 4WU2 for Canada; the companion owner's manual is labeled YFM350FWBK(C). Yamaha states that the service book was produced primarily for dealers and qualified mechanics and assumes a basic understanding of mechanical repair. The owner's book is aimed at riders performing preventive maintenance and minor repairs.

• Document set: A 485-page PDF set consisting of the 319-page YFM350FWBJ Service Manual, Yamaha literature no. LIT-11616-10-58 (first edition, November 1996), and the 166-page YFM350FWBK(C) Owner's Manual, P/N LIT-11626-10-93 (first edition, April 1997).
• Engine teardown and repair: Covers engine removal, cylinder-head and valve work, camshaft and timing-chain service, piston and crankshaft inspection, balancer and oil-pump service, primary and secondary clutch work, transmission teardown and reassembly, and electric and recoil starting drives.
• Shaft-drive procedures: Details the middle gear, front differential and constant-velocity joints, rear axle and final drive, shim selection, gear-lash measurement and adjustment, and post-assembly operation checks.
• Fuel and chassis work: Walks through BST34 Mikuni carburetor disassembly and fuel-level adjustment, front and rear wheel service, hydraulic front drum-brake overhaul and bleeding, rear brake work, steering, front arms, shocks, and swingarm service.
• Electrical fault isolation: Provides system-specific checks for CDI ignition, electric starting, charging, lighting, signal circuits, and the oil-temperature warning system, backed by component test specifications and a full-machine wiring diagram.
• Owner operation and minor service: Maps control functions, shifting and reverse, cold and warm starting, loading, hills, descents, shallow water, and rough terrain, then covers scheduled attention to oils, filters, brakes, clutch, cables, battery, fuse, and lights.
• Factory reference support: Uses exploded assembly views, cable-routing drawings, lubrication diagrams, inspection limits, component torque tables, clearance and adjustment data, and numbered special tools throughout the repair procedures.

Engine and Driveline Repair Depth

The 348 cc air-cooled, four-stroke SOHC single uses a wet centrifugal automatic clutch, a constant-mesh transmission with five forward speeds and reverse, and shaft final drive. Beyond routine adjustments, the service manual carries repair work through measurement, part evaluation, reassembly, and final operating checks. Middle-drive and final-drive sections cover calculated shim selection and gear-lash setup rather than stopping at unit replacement.

Advanced jobs are tied to the specified factory tooling. Examples include crankcase separating tool YU-01135-A/90890-01135, pinion gear fix clamp YM-04129/90890-04129, gear-lash measurement tool YM-01231/90890-01231, bearing-retainer wrench YM-04128/90890-04128, and ignition checker 90890-06754. Tool identification is backed by exploded diagrams, illustrated part locations, tightening sequences, lubrication points, wear limits, and model-specific service data.

The driveline chapter warns that insufficient gear lash after reassembly can quickly destroy gear teeth, making the shim-selection and lash checks a critical part of the repair. The hydraulic brake section specifies new brake fluid rather than solvent for cleaning internal parts because solvent can swell and distort the seals.

Electrical Diagrams and Troubleshooting

Named electrical material covers the Ignition System Circuit Diagram, Electrical Starting System Circuit Diagram, Charging System Circuit Diagram, Lighting System Circuit Diagram, Signal System Circuit Diagram, and the full YFM350FWB Wiring Diagram. The related charts isolate no-spark or intermittent-spark faults, a starter that will not operate, a battery that will not charge, inoperative lamps, and neutral, reverse, or oil-temperature warning-light problems.

A separate troubleshooting chapter addresses hard starting, poor idle and high-speed performance, shaft-drive faults, hard shifting or jumping out of gear, clutch slipping and dragging, overheating, weak braking, shock-absorber trouble, and unstable handling. These charts connect symptoms to the relevant fuel, compression, electrical, drivetrain, or chassis checks without reducing the manual to a specifications catalog.

Controls, Riding, and Owner Maintenance

The owner's manual explains the main switch, indicator and handlebar controls, throttle and speed limiter, front and rear brakes, parking brake, shift pedal, reverse knob, recoil starter, fuel cock, choke, shock adjustment, and auxiliary DC terminal. Operating sections cover pre-ride checks, engine break-in, loading and towing, hill climbs and descents, side slopes, shallow-water crossings, rough ground, sliding, and recovery from stalls or loss of traction.

Its maintenance section provides the factory schedule and service record along with engine, final-drive, and differential oil work; spark-plug and air-filter care; brake, clutch, and cable adjustments; wheel removal; battery and fuse service; and headlight replacement. Yamaha directs unfamiliar owners to a dealer and reserves brake-fluid replacement for trained service personnel. Safety coverage is specific to this ATV, including off-road-only operation, secure vehicle support, moving and electrical components, hot exhaust parts, brake work, and ventilation during running-engine checks.