Yamaha Grizzly Service Manual 400

The Yamaha Grizzly 400 Service Manual is a comprehensive guide for the maintenance, repair, and troubleshooting of the Yamaha Grizzly 400 ATV. It covers the YFM400FA and YFM400FPA models, providing detailed procedures for the engine, transmission, chassis, electrical system, and periodic maintenance. This manual is intended for qualified service technicians and contains specifications, adjustment data, and safety warnings essential for proper servicing.

1. General Information 2. Periodic Maintenance 3. Specifications 4. Engine 5. Fuel System 6. Chassis 7. Electrical System 8. Troubleshooting 9. Wiring Diagrams 10. Safety Precautions 11. Index

General Information

This section includes model identification, manual organization, general safety rules, and tool requirements.

Item	Description
Model Identification	YFM400FA (2WD), YFM400FPA (4WD)
Identification Number Location	Frame left side, near the steering head
Manual Organization	Chapters divided by system (Engine, Chassis, Electrical)
Safety Symbol Meaning	WARNING, CAUTION, NOTE for hazard levels
Recommended Tools	Standard mechanic's tools, Yamaha special tools as listed

Periodic Maintenance

Lists maintenance intervals and procedures to ensure optimal performance and longevity.

Pre-ride inspection: Check tires, brakes, lights, fluid levels, and controls.
Engine oil change: Every 100 hours or 6 months; use Yamalube 4 (10W-30) or equivalent.
Oil filter replacement: Every other oil change.
Air filter service: Clean every 20 hours; replace if damaged.
Spark plug inspection: Check gap (0.6–0.7 mm) and condition every 100 hours.
Drive chain adjustment: Check slack (45–55 mm) and lubricate every 20 hours.
Brake fluid inspection: Check level and condition every 100 hours.
Valve clearance inspection: Check and adjust every 200 hours.

WARNING! Always perform maintenance in a well-ventilated area with the engine off and cool. Secure the ATV on a level surface.

Specifications

Engine Type: 4-stroke, SOHC, air-cooled, single cylinder.
Displacement: 398 cm³.
Bore x Stroke: 83.0 mm × 73.6 mm.
Compression Ratio: 8.5:1.
Starting System: Electric start with auxiliary recoil.
Transmission: 5-speed with reverse; Ultramatic® V-belt automatic.
Drive System: Yamaha On-Command® 2WD/4WD with differential lock.
Suspension Front/Rear: Independent double wishbone / Swingarm.
Brakes Front/Rear: Dual hydraulic disc / Sealed mechanical drum.
Tires Front/Rear: AT22 x 7-10 / AT22 x 10-10.
Fuel Capacity: 15.5 liters (4.1 US gal).
Oil Capacity: 2.0 liters (2.1 US qt) with filter change.

Engine

Detailed procedures for engine removal, disassembly, inspection, reassembly, and installation.

Top End: Cylinder head removal, valve service, camshaft inspection, cylinder and piston measurement. Bottom End: Crankcase splitting, crankshaft inspection, connecting rod big-end play, transmission disassembly. Lubrication System: Oil pump inspection, strainer cleaning, pressure testing.

Torque Specifications: Cylinder head bolts: 40 Nm (4.0 kgf-m, 29 ft-lb). Spark plug: 12.5 Nm (1.25 kgf-m, 9.0 ft-lb). Oil drain plug: 30 Nm (3.0 kgf-m, 22 ft-lb).

Fuel System

Covers carburetor service, fuel tank, fuel pump, and throttle operation.

Carburetor disassembly: Remove float bowl, jets, needle valve, and diaphragm.
Cleaning: Use carburetor cleaner and compressed air on all passages.
Adjustment: Pilot screw (initial setting: 2-1/4 turns out), float height (14.0 mm).
Fuel pump testing: Check for proper flow and pressure.
Throttle cable free play: Adjust to 3–5 mm at the lever.

Tip: Always use fresh fuel and stabilize fuel if storing the ATV for more than 30 days.

Chassis

Procedures for front and rear suspension, brakes, steering, wheels, and drive system.

Front suspension: A-arm removal, shock absorber service, ball joint inspection.
Rear suspension: Swingarm pivot bearing inspection and lubrication.
Brakes: Pad/shoe replacement, rotor/drum measurement, bleeding hydraulic system.
Steering: Handlebar alignment, steering stem bearing adjustment.
Drive system: V-belt inspection and replacement, On-Command system operation check.

WARNING! Support the ATV securely with jack stands before working underneath. Never rely solely on a hydraulic jack.

Electrical System

Testing and service for battery, charging system, starting system, lighting, and switches.

Component	Test/Procedure	Specification
Battery	Voltage check, load test	12.8 V (fully charged), 130 CCA
Stator Coil	Resistance check (white-white)	0.21–0.31 Ω at 20°C (68°F)
Starter Motor	Brush length inspection	Replace if less than 6.5 mm
CDI Unit	Continuity tests per chart	Refer to specific resistance values
Headlight	Voltage at connector	12 V+ with engine running

Troubleshooting

Systematic approach to diagnosing common problems.

Symptom	Possible Cause	Corrective Action
Engine does not start	Weak battery, faulty spark, fuel issue	Check battery voltage, spark plug, fuel flow to carb.
Engine starts but dies	Clogged pilot jet, vacuum leak	Clean carburetor, inspect intake manifold.
Poor performance/loss of power	Dirty air filter, worn drive belt	Service air filter, inspect belt for wear/cracks.
Excessive vibration	Unbalanced wheels, engine mount loose	Check tire balance, tighten all engine mounts.
4WD not engaging	Faulty actuator, wiring issue	Test On-Command actuator, check switch and connections.
Brakes dragging or weak	Contaminated pads, air in line, worn shoes	Clean or replace pads/shoes, bleed brake system.

Wiring Diagrams

Complete color-coded wiring diagrams for the entire electrical system, including connector locations and ground points.

CAUTION! Disconnect the negative battery terminal before performing any electrical work to prevent shorts or ECU damage.

Safety Precautions

Essential safety practices for the technician and to ensure vehicle safety post-service.

Always wear safety glasses and appropriate gloves.
Use only Yamaha Genuine Parts or equivalents meeting Yamaha specifications.
After reassembly, double-check all fasteners for proper torque.
Test ride the ATV in a safe, controlled area after major service to verify operation.
Properly dispose of used fluids (oil, coolant) and filters according to local regulations.

Index

Alphabetical listing of major components and procedures for quick reference.

Air Filter, 3-4
Battery, 8-1
Brakes, 7-5
Carburetor, 6-2
Drive Belt, 7-10
Electrical Diagram, 10-1
Engine Removal, 5-3
Oil Change, 3-2
Specifications, 4-1
Troubleshooting, 9-1
Valve Clearance, 3-8
Wheel Removal, 7-8