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

Use the service procedures for internal repairs and fault isolation, and the owner's guidance for operation, riding and preventive maintenance.

The front differential chapter covers case, bearing, ring-gear and lash work, but Yamaha instructs against dismantling the factory-assembled differential unit itself.

PDF Search, Bookmarks and Wiring Detail

Search and diagram detail: Both PDFs have OCR text search and embedded bookmarks, with recognition errors in some diagram labels. Small wiring codes need zooming; shaded circuit diagrams are grainier than the full-machine diagram. The owner's final bookmark is mislabeled and opens the warranty section.

ZIP download containing two printable English PDFs, totaling 485 pages. This includes covers, front matter and eight administrative and supplementary pages: one in the service PDF and seven in the owner's PDF.

Engine, Shaft-Drive and Owner Coverage

These selected topics outline the main work covered. Additional subjects include cleaning and long-term storage.

• Engine repair: Air-cooled single-cylinder engine removal, cylinder-head and valve work, camshaft and timing-chain service, piston and crankshaft inspection, balancer and oil-pump repair.

• Clutch and starting drives: Wet centrifugal automatic clutch inspection, primary and secondary clutch work, transmission teardown and reassembly, and electric and recoil starting drives.

• Shaft drive: Middle gear, front differential, constant-velocity joints, rear axle and final drive, including shim selection, gear-lash adjustment and operating checks.

• Carburetion: BST34 Mikuni carburetor removal, disassembly, component inspection and reassembly, with float-height and fuel-level adjustment procedures.

• Brakes and chassis: Hydraulic front drum-brake overhaul and bleeding, rear drum-brake work, front and rear wheel service, steering, front arms, shock absorbers and swingarm.

• Electrical diagnosis: CDI ignition, starting, charging, lighting, signal and oil-temperature warning circuits, with component tests, fault-isolation charts and wiring diagrams.

• Owner operation and care: Pre-ride checks, cold and warm starting, shifting and reverse, loading and towing, plus engine, final-drive and differential oil care.

Yamaha wrote the service volume primarily for dealers and qualified mechanics with a basic understanding of mechanical repair; the owner's book addresses preventive maintenance and minor repairs.

Engine Inspection and Driveline Setup

Repair sections carry work through measurement, wear-limit checks, part evaluation, reassembly and final operating checks. Exploded assembly views, cable-routing drawings and lubrication diagrams support the procedures, alongside component torque tables, clearances and tightening sequences.

Factory tooling: Engine work identifies crankcase separating tool YU-01135-A/90890-01135. Driveline procedures specify pinion gear fix clamp YM-04129/90890-04129, gear-lash measurement tool YM-01231/90890-01231 and bearing-retainer wrench YM-04128/90890-04128.

Middle-drive and final-drive setup uses component markings to calculate shim thicknesses. Rear final-drive work also covers thrust-washer and ring-gear-stopper selection. Yamaha warns that insufficient gear lash can destroy the gear teeth after reassembly.

Carburetor, Brakes and Suspension

Carburetor inspection distinguishes piston-valve, coasting-enricher diaphragm and needle-valve faults from float-setting problems. The hydraulic brake section warns that solvent on internal brake components can swell and distort the seals.

Chassis procedures include wheel-bearing replacement, tie-rod and steering-shaft inspection, toe-in adjustment and swingarm-bearing evaluation. Shock-absorber checks lead to assembly replacement for leakage, bent rods or fatigued springs.

Circuit Diagrams and Fault Isolation

System-specific test charts support diagnosis before component replacement. For example, the starter checks distinguish motor faults from relay, switch or wiring problems; ignition testing identifies ignition checker 90890-06754.

The Ignition System Circuit Diagram, Electrical Starting System Circuit Diagram and Charging System Circuit Diagram accompany no-spark, inoperative-starter and battery-not-charging checks.

The Lighting System Circuit Diagram, Signal System Circuit Diagram and full YFM350FWB Wiring Diagram support lamp, neutral, reverse and oil-temperature warning-light diagnosis.

Separate symptom charts address hard starting, poor idle and high-speed performance, hard shifting or jumping out of gear, and clutch slipping or dragging. They also cover shaft-drive faults, overheating, weak braking, shock-absorber trouble and unstable handling.

Controls, Riding and Owner Maintenance

The control reference explains the main switch, indicator and handlebar controls, throttle and speed limiter, front and rear brakes, parking brake, shift pedal and reverse knob. It also covers the recoil starter, fuel cock, choke, shock adjustment and auxiliary DC terminal.

Riding guidance covers engine break-in, hill climbs and descents, side slopes, shallow water, rough ground, sliding, and recovery from stalls or loss of traction.

The maintenance schedule and service record accompany 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 addresses off-road-only operation, secure vehicle support, moving and electrical components, hot exhaust parts, brake work and ventilation during running-engine checks.

A Preview of Valve and Carburetor Settings

Cold valve-clearance specifications are 0.06–0.10 mm intake and 0.16–0.20 mm exhaust. The adjustment section identifies compression-stroke top dead center as the checking condition.

For the BST34 Mikuni carburetor, the fuel-level specification is 2.0–3.0 mm above the float-chamber mating surface. The chapter distinguishes this gauge reading from float-height measurement and provides the related inspection and adjustment procedures.