Market Segment:
High-performance off-road/enduro motorcycle.
Target Audience:
Enthusiasts, off-road riders, mechanics specializing in dirt bikes.
Competitors Era:
Honda CR series, KTM EXC series, Suzuki RM-Z/RMX series, Kawasaki KX series.
Vehicle Focus:
Lightweight, powerful, off-road capable, liquid-cooled 4-stroke engine.
Manual Value Proposition:
Enables owners and technicians to perform all necessary maintenance and repairs, ensuring optimal performance and longevity of the WR400F.
Engine:
Comprehensive coverage including disassembly, inspection, assembly, tuning, lubrication, cooling, and fuel systems.
Transmission:
Clutch, gearbox, shift mechanism, and related components.
Chassis:
Frame, suspension (front forks, rear shock), steering, swingarm, and hubs.
Electrical System:
Ignition system, lighting, charging system (stator, regulator/rectifier), battery, wiring diagrams, troubleshooting.
Fuel System:
Carburetor (Mikuni VM series), fuel tank, fuel lines, and filters.
Braking System:
Front and rear disc brakes, hydraulic systems, pad replacement, fluid bleeding.
Exhaust System:
Muffler, header pipe, and heat shields.
Cooling System:
Liquid cooling system, radiator, hoses, water pump, coolant specifications.
Bodywork:
Body panels, seat, fenders, and mounting hardware.
Routine Maintenance:
Oil changes, filter replacement, chain adjustment, spark plug service, air filter cleaning/replacement.
Engine Rebuild:
Top-end rebuild (piston, rings, cylinder), bottom-end procedures (crankshaft, bearings, seals), valve adjustments.
Troubleshooting:
Diagnostic procedures for common issues, electrical faults, engine performance problems.
Suspension Service:
Fork seal replacement, fork oil change, rear shock service, linkage maintenance.
Brake Service:
Brake pad replacement, caliper service, master cylinder service, brake line replacement, bleeding procedure.
Carburetor Tuning:
Adjustment of idle speed, jetting recommendations, float bowl service.
Electrical Diagnostics:
Using multimeters, checking circuits, troubleshooting ignition and charging faults.
Wheel And Tire Service:
Spoke tensioning, wheel bearing replacement, tire changes.
Depth:
Comprehensive, covering from basic owner maintenance to complete engine and chassis overhauls. Detailed torque specifications, clearances, and diagnostic flowcharts.
Engine Type:
4-stroke, DOHC, 5-valve, Liquid-cooled
Bore X Stroke:
84.0 mm x 70.0 mm
Compression Ratio:
12.0:1
Lubrication System:
Wet sump with oil cooler
Horsepower Estimated:
~40-45 HP (at crankshaft, estimated)
Torque Estimated:
~38-40 Nm (at crankshaft, estimated)
Carburetor Model:
Mikuni VM36SS
Fuel Type:
Unleaded gasoline, minimum 91 octane (RON+MON)/2 = 87 AKI
Ignition System:
CDI (Capacitor Discharge Ignition)
Cooling Method:
Liquid-cooled
Coolant Type:
Yamaha All Weather Coolant or equivalent silicate-free, ethylene glycol based coolant
Safety Ratings:
N/A (Off-road motorcycle, not subjected to standard automotive crash testing.)
Braking:
Hydraulic disc brakes front and rear for effective stopping power.
Suspension:
Long-travel, adjustable suspension (Kayaba) for terrain absorption and control.
Lighting:
Headlight and taillight for visibility.
Frame Construction:
Strong steel perimeter frame for chassis rigidity and rider feedback.
Engine Oil Change:
Every 1,000 km (600 miles) or 3 months, whichever comes first. More frequently for demanding use.
Oil Filter Replacement:
Every 2,000 km (1,200 miles) or 6 months.
Air Filter Cleaning:
Every 500 km (300 miles) or 1 month (clean and re-oil). Replace if damaged.
Spark Plug Inspection:
Every 1,000 km (600 miles).
Valve Clearance Check:
Every 4,000 km (2,500 miles) or 12 months.
Chain Lubrication Adjustment:
Every 500 km (300 miles) or 1 month.
Engine Oil Grade:
SAE 10W-40
Engine Oil Capacity:
Approx. 1.80 Liters (1.90 US qt) without filter change, 1.90 Liters (2.00 US qt) with filter change.
Brake Fluid:
DOT 3 or DOT 4 hydraulic brake fluid.
Coolant Type:
Yamaha All Weather Coolant or equivalent silicate-free, ethylene glycol based coolant.
Common Wear Items:
Piston rings, valve seals, clutch plates, wheel bearings, fork seals.
Engine Performance Quirks:
Can be prone to minor carburetor tuning adjustments due to altitude or temperature changes. Valve seat wear can occur with very high mileage or improper maintenance.
Electrical Notes:
While generally reliable, check grounds and connections, especially in off-road environments where moisture and dirt can ingress.
Brand Focus:
Yamaha has a long-standing reputation for producing high-performance motorcycles across various disciplines, including off-road and motocross.
Predecessor:
Evolved from Yamaha's successful 2-stroke off-road models, offering a 4-stroke alternative with improved torque and tractability.
Segment Introduction:
The WR-F series was Yamaha's answer to the growing demand for competitive 4-stroke enduro motorcycles in the late 1990s.
Production Period:
The WR400F was produced from 1998 to 2000, before being succeeded by the WR426F.
