Yamaha Grizzly 450 Service Manual

The Yamaha Grizzly 450 is a rugged all-terrain vehicle (ATV) designed for utility and recreational use. This service manual provides comprehensive information for maintenance, troubleshooting, and repair of the Grizzly 450, including engine specifications, chassis details, electrical systems, and periodic maintenance procedures. Below are key sections covering safety, specifications, maintenance schedules, component service, and troubleshooting.

Features at a Glance

Key components: 421cc liquid-cooled, 4-stroke engine, Ultramatic automatic transmission with engine braking, On-Command 2WD/4WD with differential lock, independent double-wishbone front suspension, and a durable steel frame.

Safety Precautions

Always follow safety procedures when servicing the ATV.

1. Work in a well-ventilated area; keep away from open flames.
2. Disconnect battery negative terminal before electrical work.
3. Use proper tools and torque specifications.
4. Support ATV securely on a stand or lift; never work under unsupported vehicle.
5. Wear safety glasses and gloves when handling fluids or sharp components.

WARNING! Engine and exhaust components become extremely hot; allow to cool before servicing. Always relieve fuel system pressure before disconnecting fuel lines.

Specifications

• Engine: 421cc, liquid-cooled, 4-stroke, SOHC, 4-valve.
• Bore x Stroke: 83.0 mm x 77.0 mm.
• Compression Ratio: 9.5:1.
• Fuel System: Mikuni BSR33 carburetor.
• Ignition System: DC-CDI.
• Starting System: Electric start with auxiliary recoil.
• Lubrication System: Wet sump.
• Transmission: Ultramatic automatic V-belt with H, L, N, R, P ranges.
• Final Drive: Shaft drive.
• Dimensions (LxWxH): 81.5 in x 46.1 in x 48.4 in.
• Ground Clearance: 10.0 in.
• Dry Weight: 595 lbs.

Maintenance Schedule

Refer to the following intervals for routine maintenance (based on normal operating conditions).

Note: Severe use (mud, dust, towing) requires more frequent maintenance.

Engine Service

Procedures for engine disassembly, inspection, and reassembly.

1. Oil Change: Warm engine, drain oil, replace filter, refill with 2.6 qt of SAE 10W-30 or 10W-40 (API SG or higher).
2. Valve Clearance: Check cold: Intake 0.10–0.15 mm, Exhaust 0.15–0.20 mm.
3. Cylinder Head Removal: Remove camshaft, check for warpage (limit 0.03 mm).
4. Piston & Rings: Measure ring end gap (top: 0.15–0.30 mm, second: 0.15–0.30 mm, oil: 0.20–0.70 mm).
5. Crankshaft & Connecting Rod: Check big-end side clearance (limit 0.35 mm).

Torque Specs: Cylinder head bolts: 20 Nm (14.8 ft-lb) in crisscross pattern. Spark plug: 13 Nm (9.4 ft-lb).

Chassis & Suspension

Service procedures for frame, suspension, and brakes.

1. Front Suspension: Inspect A-arms, bushings, and ball joints for wear. Replace if loose.
2. Rear Suspension: Check swingarm pivot bearings; lubricate every 500 mi.
3. Steering: Adjust steering stem bearing preload; check for smooth movement.
4. Brakes: Pad wear limit: 1.0 mm. Brake fluid: DOT 4. Bleed system if spongy.
5. Tires: Pressure: 3.5 psi (front), 3.5 psi (rear) for standard use. Inspect for cuts/wear.

Wheel Removal: Torque lug nuts to 55 Nm (40 ft-lb) in crisscross pattern.

Electrical System

Testing and service of battery, charging system, and ignition.

1. Battery: 12V, 12Ah. Maintain voltage above 12.6V. Clean terminals regularly.
2. Charging System: Stator resistance: 0.36–0.54 Ω (20°C). Regulator/rectifier output: 13.5–15.5V at 5000 rpm.
3. Starter: Draw current: less than 90A. Brush length limit: 5.5 mm.
4. Ignition Coil: Primary: 0.56–0.84 Ω, Secondary: 6.65–9.95 kΩ.
5. Spark Plug: NGK CR7E, gap: 0.6–0.7 mm.

Fuses: Main 30A, Headlight 10A, Signal 10A, Ignition 10A. Always replace with same rating.

Fuel System

Carburetor service and fuel delivery.

1. Carburetor: Mikuni BSR33. Pilot screw initial setting: 2 turns out. Float height: 13.0 mm.
2. Fuel Valve: Inspect for leaks; clean sediment cup.
3. Fuel Pump: Flow rate: >100 cc per 30 seconds at cranking.
4. Throttle Cable: Adjust free play: 3–5 mm at lever.
5. Choke: Ensure smooth operation; clean plunger if sticky.

Jet Sizes (standard): Main jet #130, Pilot jet #42.5, Needle jet: N/A.

Transmission & Drivetrain

Ultramatic transmission and differential service.

1. Drive Belt: Width limit: 27.9 mm. Inspect for cracks/glazing.
2. Clutch Sheaves: Clean with compressed air; check for wear on movable sheave face.
3. Differential Oil: Capacity: 0.35 qt. Replace with SAE 80W-90 API GL-5.
4. Drive Shaft: Inspect U-joints for play; lubricate splines every 500 mi.
5. On-Command System: Test 2WD/4WD engagement; check vacuum lines for leaks.

Shift Mechanism: Adjust linkage if shifting is stiff or inaccurate.

Troubleshooting

Note: Always diagnose systematically; refer to specific sections for detailed procedures.

Wiring Diagrams

Complete electrical schematics for the Grizzly 450 are included in the manual appendix. Diagrams cover:

• Main harness routing and connectors.
• Ignition and charging system circuits.
• Lighting and switch connections.
• On-Command 4WD system wiring.
• Ground point locations.

Use: For accurate diagnosis, refer to the full-color diagrams in the printed manual or PDF.

Service Support: For genuine parts and technical assistance, contact Yamaha Motor Corporation at 1-800-962-7926 or visit www.yamahamotorsports.com.