Model Variants Covered:
YFM400FP Big Bear 4WD, YFM400FWR Big Bear 4WD, YFM40FS Big Bear 4X4, YFM40FT Big Bear 4WD, YFM40FV Big Bear 4WD, YFM400FWNP Big Bear, YFM400FWNM(C) Big Bear, YFM400FM(C) Big Bear
Production Years Covered:
2002, 2003, 2004, 2005, 2006 (manual also covers 1999-2001 models)
Vehicle Type:
Utility ATV (all-terrain vehicle)
Target Audience:
Recreational riders, farmers, ranchers, hunters and utility users needing a dependable 4x4 work ATV
Key Advantage:
Simple, durable drivetrain with shaft drive andSelectable 2WD/4WD, easy to service with basic tools
Powertrain:
401cc single-cylinder engine with 5-speed transmission and reverse
Drivetrain:
4WD with shaft final drive
Manual Type:
Factory service repair manual (1 main manual plus 2 supplementary manuals)
Coverage Areas:
Complete vehicle: general information, maintenance, fuel system, cooling system, engine, transmission, clutching, final drive, body and frame, steering and suspension, brakes, electrical, wiring diagrams
Page Count:
N/A - not specified, multi-hundred page combined set
Delivery Method:
Instant digital download after payment
Software Required:
None - any standard PDF viewer works
Printed Appearance:
Identical to a printed repair book sold in stores
General Information:
Vehicle identification, specifications, special tools, torque values
Maintenance:
Scheduled service, adjustments, lubrication points
Fuel System:
Carburetor, fuel tank, throttle, disassembly and tuning
Cooling System:
Fan-cooled engine cooling components
Engine:
Complete top-end and bottom-end removal, disassembly, inspection, rebuild
Transmission:
Transmission gears, shafts and shifting mechanism service
Clutching:
Wet multi-plate clutch removal, inspection and adjustment
Final Drive:
Shaft drive differentials, front and rear gear cases
Body and Frame:
Fenders, racks, frame components
Steering and Suspension:
Front and rear suspension, steering stem, shocks
Brakes:
Front and rear brake systems, drums, pads, cables
Electrical:
Ignition, charging, starting, lighting circuits
Wiring Diagrams:
Full-color wiring schematics for all covered model years
Procedure Style:
Detailed step-by-step removal, disassembly, inspection and installation instructions
Chapter Intros:
Each chapter opens with assembly or system illustrations, exploded views and pictures
Troubleshooting:
Troubleshooting section for each system plus overall diagnostics
Specifications:
Service specifications, tightening torques and inspection limits per chapter
Technical Depth:
Full teardown to component level, suitable for complete engine rebuilds
Parts Information:
Exploded parts diagrams showing component relationships and part orientation
Audience:
Professional technicians and DIY owners
File Format:
PDF (searchable, bookmarked, zoomable)
Compatibility:
Windows, macOS, Linux, iOS, and Android — any device with a PDF reader
Requirements:
A PDF reader application (e.g. Adobe Acrobat Reader, free)
Searchability:
Fully text searchable for fast lookup of any topic
Print Quality:
High-resolution digital pages, printable at full clarity
Binding Type:
N/A — digital download, no physical binding
Paper Type:
N/A — digital download, no physical paper
Primary Engine:
401cc (24.4 cu in) air/oil-cooled SOHC single-cylinder 4-stroke
Bore and Stroke:
83.0 mm bore x 74.0 mm stroke (nominal factory figures)
Carburetor:
Mikuni constant-velocity carburetor
Fuel System:
Carbureted, regular unleaded gasoline
Cooling:
Oil-cooled with cooling fan
Starting System:
Electric start with recoil backup
Standard Transmission:
5-speed constant-mesh manual with reverse and automatic clutch
Drivetrain:
Selectable 2WD/4WD with shaft final drive
Features:
Dual-range... N/A - not specified for this model
Manual Coverage:
Complete transmission, clutch and final drive rebuild procedures
Audio System:
N/A - utility ATV, not equipped with audio system
Utility & Driver Assistance
Instrumentation:
Speedometer and indicator lights
Driver Assistance:
N/A - no electronic driver assistance on this model
Electrical Outlets:
N/A - not specified for this model
Scheduled Service:
Full maintenance schedules and adjustment charts included in the manual
Typical Intervals:
Oil change every 100 operating hours or as listed in the periodic maintenance table
Valve Clearance:
Periodic valve lash inspection and adjustment procedure included
Engine Oil:
Yamalube 4-stroke oil or equivalent API SE or higher SAE per temperature chart
Final Gear Case Oil:
SAE 80 API GL-4 hypoid gear oil (front and rear cases)
Brake Fluid:
Drum brake system - no hydraulic fluid required
Known Issues / Common Wear
Common Wear Items:
Brake shoes, drive chain-free shaft drive U-joints, air filter, spark plug, clutch plates
Carburetor:
Periodic carburetor cleaning and tuning covered step by step
Manufacturer:
Yamaha Motor Company, Japan
Big Bear Lineage:
Big Bear 350 introduced 1987, growing into the Big Bear 400 for more torque and utility capability
Generation Covered:
1999-2006 Big Bear 400 generation, sold as YFM400 4WD variants
Production Location:
Yamaha manufacturing facilities in Japan
