Category:
Off-Road Motorcycle
Segment:
Enduro/Motocross
Key Competitors:
KTM EXC series, Honda CRFX series, Suzuki RMZ series, Kawasaki KXFX series
Unique Selling Points:
Yamaha's robust 5-valve titanium cylinder head design, reliable engine performance, and excellent handling characteristics for its class.
Target Audience:
Motocross and enduro riders seeking a durable, high-performance off-road machine, and home mechanics performing maintenance and repairs.
Engine:
Complete engine disassembly, assembly, inspection, and repair (including top-end, bottom-end, cooling system, lubrication)
Fuel System:
Carburetor service and adjustment, fuel tank, fuel lines, fuel pump (if applicable)
Transmission:
Gearbox disassembly, inspection, and repair, clutch operation and adjustment
Drivetrain:
Chain and sprocket maintenance, rear hub, wheel bearings
Suspension:
Front fork service (oil changes, seal replacement, component inspection), rear shock absorber inspection and service, linkage maintenance
Brakes:
Hydraulic brake system maintenance (front and rear calipers, master cylinders, brake lines), bleeding procedures, pad and rotor inspection
Electrical System:
Ignition system troubleshooting, lighting, charging system (stator, rectifier/regulator), wiring diagrams, battery maintenance
Cooling System:
Radiator service, coolant replacement, hose inspection, water pump inspection
Frame And Bodywork:
Chassis inspection, plastic body panel removal and installation, seat, fuel tank removal and installation
Wheels And Tires:
Tire inspection, spoke tensioning, rim maintenance
Maintenance:
Routine maintenance checks, oil changes, filter replacements, lubrication points, chain adjustment, air filter cleaning/replacement
Troubleshooting:
Diagnostic charts for common problems (starting issues, poor performance, electrical faults)
Repair:
Step-by-step procedures for component removal, overhaul, and reassembly
Overhaul:
Detailed procedures for engine and transmission overhauls
Specifications:
Torque specifications for all fasteners, engine build clearances, fluid capacities
Adjustment:
Carburetor tuning, clutch and throttle cable adjustments, suspension sag adjustment
Wiring Diagrams:
Detailed electrical system wiring diagrams included for accurate troubleshooting.
Depth Level:
Comprehensive (covers everything from basic maintenance to full engine rebuilds and advanced diagnostics)
Detail Level:
Highly detailed with exploded views, diagrams, and step-by-step instructions suitable for professional mechanics and experienced enthusiasts.
File Format:
PDF (most common for digital manuals, allows for searchability and easy printing)
Searchability:
Searchable text for quick information retrieval
Print Quality:
High-resolution images and clear text, suitable for printing individual pages or the entire document.
Binding Type:
N/A (Digital Format)
Paper Type:
N/A (Digital Format)
Manual Type Detail:
Comprehensive workshop manual for diagnosis, repair, and maintenance. Not an owner's manual.
Engine Type:
4-stroke, liquid-cooled, DOHC, 5-valve
Displacement:
400cc (WR400F) / 426cc (WR426F)
Bore X Stroke:
WR400F: 89.0 x 63.7 mm; WR426F: 95.0 x 61.2 mm
Compression Ratio:
WR400F: 12.0:1; WR426F: 12.5:1 (Typical for these models)
Horsepower Estimate:
Approximately 50-55 hp (at crank), depending on tune and model.
Torque Estimate:
Approximately 30-35 lb-ft (at crank), depending on tune and model.
Carburetor:
Keihin FCR flatside carburetor (e.g., FCR 39mm)
Fuel Type:
Unleaded gasoline, 91 octane or higher recommended.
Fuel Tank Capacity:
Approximately 2.5 gallons (9.5 Liters)
Transmission Type:
5-speed constant mesh manual
Clutch Type:
Wet, multiple-disc, cable-actuated
Gear Ratios:
Specific gear ratios would be detailed in the manual, but are optimized for off-road performance.
Transmission Oil Type:
Yamaha's recommended 10W-40 or 20W-40 motorcycle oil (often shared with engine oil in 4-strokes)
Transmission Oil Capacity:
Approximately 0.8 - 1.0 Liters (check manual for exact specification)
Length:
Approximately 83.7 inches (2125 mm)
Width:
Approximately 32.3 inches (820 mm)
Height:
Approximately 50.2 inches (1275 mm)
Wheelbase:
Approximately 57.7 inches (1465 mm)
Dry Weight:
Approximately 240-245 lbs (109-111 kg)
Wet Weight:
Approximately 255-260 lbs (116-118 kg) (with fluids)
Ground Clearance:
Approximately 13.4 inches (340 mm)
Engine Oil Change:
Every 10-15 hours of riding or every 3 months (severe use); longer for casual use (refer to manual for precise recommendations).
Air Filter Cleaning:
After every few rides, or more frequently in dusty conditions.
Chain Lubrication:
Every 500-700 km or whenever dry.
Spark Plug Inspection:
Every 10-15 hours of riding.
Valve Clearance Check:
Every 15-20 hours of riding or annually.
Engine Oil:
Yamalube 4 10W-40 or equivalent API SG or higher (check manual for specific viscosity and API rating).
Coolant:
Permanent type anti-freeze coolant (ethylene glycol based), 50% mixture with distilled water.
Brake Fluid:
DOT 4 hydraulic brake fluid.
Common Wear Items:
Clutch plates, wheel bearings, fork seals, chain and sprockets, piston rings.
Potential Failures:
While generally robust, issues can arise from improper maintenance, such as overheating due to coolant leaks or engine damage from poor lubrication. Carburetor jetting can also be sensitive to altitude and modifications.
Manufacturer:
Yamaha Motor Company is renowned for its innovation and performance in motorcycles, particularly in off-road and racing applications.
Predecessor:
The WR400F was a successor to earlier Yamaha 2-stroke off-road models and a predecessor to the highly successful WR450F. The WR426F was a short-lived but powerful iteration in the lineage.
Generation Notes:
The WR400F and WR426F represented Yamaha's strong entry into the 4-stroke off-road racing and trail riding segment, competing directly with other manufacturers' premium offerings.
Production Period:
The WR400F was produced from 1998-2000, and the WR426F from 2001-2002. This manual specifically covers the 2001 model year, which introduced the WR426F.
