🏷️ Basic Information

Make:

Yamaha

Model:

WR400F / WR426F

Year:

2002

Product Name:

Now Yamaha WR400F WR426F 2002 02 WR 400F 426F Service Repair Workshop Manual

Chassis Codes:

4WD-24510-00 (WR400F), 5JW-24510-00 (WR426F)

Manual Identifier:

Likely based on Yamaha's internal service manual numbering scheme for the model year.

👋 Introduction

Category:

High-performance off-road competition motorcycle (Enduro/Motocross).

Target Audience:

Competitive riders, serious off-road enthusiasts, and professional mechanics specializing in off-road Yamaha models.

Competitors 2002:

KTM EXC series, Honda CRFX series, Kawasaki KXF series, Suzuki RM-Z series.

Engine Type:

Liquid-cooled, four-stroke, DOHC, 5-valve (per cylinder).

Suspension Type:

High-performance adjustable front forks (likely KYB SSS) and Monoshock rear suspension (Monocross).

Manual Value Proposition:

Provides the essential technical knowledge for maintaining, diagnosing, and repairing the 2002 WR400F/WR426F, ensuring optimal performance and longevity.

📋 Manual Details

Primary Coverage:

Complete service, repair, and workshop procedures for the 2002 Yamaha WR400F and WR426F models.

Secondary Coverage Mention:

Reference to other year manuals (98-99 WR400F) indicates the potential for broader model-specific technical documentation.

Estimated Page Count:

Typically 300-500 pages for a comprehensive service manual of this era and complexity.

Type:

Service Repair Workshop Manual

Language:

English (Standard for official Yamaha service manuals of this period)

Format:

Likely a digital format (PDF) given the product listing, but original may have been printed.

📖 Manual Coverage

Engine:

Complete engine overhaul, diagnosis, tuning, performance modifications, component breakdown (carburetor, ignition, cooling, lubrication).

Transmission:

Clutch operation, gearbox disassembly/assembly, shift mechanism, lubrication, troubleshooting.

Suspension:

Front fork (KYB SSS or similar) maintenance, fork seal replacement, damper rod adjustments, rear shock absorber service, linkage lubrication.

Brakes:

Hydraulic front and rear brake systems, caliper overhaul, master cylinder service, bleeding procedures, pad replacement, rotor inspection.

Electrical System:

Wiring diagrams, lighting system, ignition system (CDI), charging system (stator, rectifier), battery maintenance, troubleshooting electrical faults.

Fuel System:

Carburetor identification (likely Mikuni VM series), jetting, float bowl adjustment, fuel tank, fuel lines, fuel filter.

Cooling System:

Radiator, hoses, coolant, thermostat (if applicable), fan operation (if equipped).

Frame And Bodywork:

Frame inspection, body panel removal/installation, seat, fuel tank mounting, footpegs, handlebars.

Wheels And Tires:

Wheel bearing maintenance, spoke tensioning, tire replacement, wheel balancing.

Routine Maintenance:

Oil changes, filter replacements, chain adjustment and lubrication, air filter cleaning, spark plug replacement.

Troubleshooting:

Diagnostic flowcharts, symptom-based problem-solving for engine, electrical, and chassis issues.

Rebuilds:

Complete engine rebuilds, carburetor overhauls, suspension component rebuilds.

Adjustments:

Valve clearance adjustments, carburetor idle and mixture adjustments, clutch and throttle cable adjustments.

Torque Specifications:

Detailed torque values for all critical fasteners.

Depth:

Comprehensive, covering from basic maintenance to complete engine and chassis overhauls. Suitable for professional mechanics and advanced DIY enthusiasts.

📊 Manual Specifications

Format:

PDF (Assumed for digital product). Searchable text is a desirable feature.

Quality:

High resolution for clear diagrams and text if digital. Original print quality would be professional offset printing.

Original Binding:

Typically a professional softcover or spiral-bound for ease of use on a workbench.

Original Paper:

Durable, often coated paper to withstand workshop environments.

⚙️ Engine Specifications

Type:

Liquid-cooled, four-stroke, DOHC, single-cylinder

Bore X Stroke 400:

81.0 mm x 77.0 mm (WR400F)

Bore X Stroke 426:

95.0 mm x 60.1 mm (WR426F)

Displacement 400:

399 cc (WR400F)

Displacement 426:

426 cc (WR426F)

Compression Ratio:

12.2:1 (Typical for this era)

Valve Train:

DOHC, 5 valves

Horsepower Estimated:

Approximately 45-50 HP (at crankshaft), specific figures vary by tuning and region.

Torque Estimated:

Approximately 30-35 lb-ft (at crankshaft), specific figures vary.

Carburetor:

Mikuni VM38SS (or similar 38mm flat-slide carburetor)

Fuel Type:

Unleaded gasoline, 91-98 octane (RON+MON)/2

Fuel Capacity:

2.6 US gallons (9.8 L)

System:

CDI (Capacitor Discharge Ignition)

System:

Wet sump

System:

Liquid-cooled with radiator and fan.

🔧 Transmission

Type:

Constant mesh, 5-speed

Clutch:

Wet, multi-plate

Gear Ratios:

Specific ratios available in the manual; designed for off-road performance.

Final Drive:

Chain drive

Transmission Oil:

Yamalube 4 (or equivalent motorcycle transmission oil), SAE 10W-30 or 20W-40 depending on temperature.

📐 Dimensions

Length:

Approx. 2,165 mm (85.2 in)

Width:

Approx. 815 mm (32.1 in)

Height:

Approx. 1,235 mm (48.6 in)

Wheelbase:

Approx. 1,475 mm (58.1 in)

Dry Weight:

Approx. 112 kg (247 lbs)

Wet Weight:

Approx. 117 kg (258 lbs) (with all fluids)

Ground Clearance:

Approx. 330 mm (13.0 in)

Seat Height:

Approx. 970 mm (38.2 in)

🛡️ Safety Features

Safety Standards:

Designed for off-road competition, not street legal. Safety features are rider-dependent and relate to component integrity and maintenance.

Brakes:

Powerful hydraulic disc brakes front and rear for effective stopping power.

Frame Construction:

Sturdy steel frame designed to withstand rigorous off-road use.

💡 Technology Features

Features:

N/A (Competition motorcycle; typically no infotainment features).

Features:

N/A (No electronic rider aids like ABS or traction control on this model).

Features:

N/A (No connectivity features).

Onboard Diagnostics:

Limited; relies on visual inspection, manual checks, and diagnostic flowcharts within the service manual. No OBD-II port.

🔧 Maintenance

Oil Change:

Every 1,000 km (600 miles) or 3 months. Frequent checks are recommended for heavy use.

Air Filter:

Clean every 5-10 riding hours or as needed based on dust conditions. Replace filter element periodically.

Chain Lubrication:

Every 500 km (300 miles) or after washing/riding in wet conditions.

Valve Clearance Check:

Every 6,000 km (3,750 miles) or as per manual recommendation.

Spark Plug Replacement:

Every 3,000 km (1,875 miles) or as needed. Recommended plug: NGK CR9E or similar.

Engine Oil Type:

Yamalube 4 (or equivalent motorcycle engine oil), SAE 10W-30 or 20W-40 (check manual for temperature suitability).

Engine Oil Capacity:

Approx. 1.0 L (1.1 US qt) with oil filter change.

Coolant Type:

Permanent type antifreeze (50% mixture with distilled water).

Carburetor Performance:

Can be sensitive to jetting changes; proper tuning for altitude and conditions is crucial. Diaphragms can wear over time.

Clutch Wear:

Aggressive riding can lead to clutch wear; fluid level and lever free play are important checks.

Suspension Seals:

Fork seals can occasionally leak due to the demands of off-road riding.

Decarbonization:

Periodic engine decarbonization recommended to maintain performance and prevent issues like stuck rings or valves.

📚 Vehicle History

Yamaha Offroad Legacy:

Yamaha has a long and successful history in off-road racing, particularly with its YZ and WR series, known for innovation and durability.

Wr400F To Wr426F Transition:

The WR400F was a groundbreaking model. The introduction of the WR426F in 2000 represented a displacement increase to enhance torque and low-end power, making it more competitive in the 4-stroke enduro class. The 2002 model likely featured refinements based on previous years' feedback.

Production Era:

Late 1990s through early 2000s, with the WR426F specifically produced from 2000 to 2002 before being replaced by the WR450F.

🏆 Awards & Recognition

Historical Reputation:

The WR series, including the WR400F and WR426F, were highly regarded in their time for their potent four-stroke power and competitive performance in enduro events.