Grizzly 450 Service Manual
The Grizzly 450 Service Manual provides comprehensive maintenance, repair, and troubleshooting information for the Yamaha Grizzly 450 ATV. This manual covers the 4x4 utility vehicle's engine, transmission, electrical system, chassis, brakes, and periodic maintenance procedures. Essential for technicians and owners performing service, it includes specifications, torque values, wiring diagrams, and step-by-step repair instructions.
General Information
This manual is intended for qualified service technicians. It provides safety information, model identification, and general service procedures for the Yamaha Grizzly 450 4x4 ATV.
| Item | Description |
|---|
| Model | Yamaha Grizzly 450 4x4 (YFM45F) |
| Vehicle Type | All-Terrain Vehicle (ATV) |
| Intended Use | Utility, Recreational |
| Manual Purpose | Service, Repair, Maintenance |
| Safety Symbols | WARNING, CAUTION, NOTE explained |
Specifications
- Engine Type: 4-stroke, SOHC, air-cooled, 4-valve.
- Displacement: 421 cc.
- Bore x Stroke: 87.5 mm x 70.0 mm.
- Compression Ratio: 9.2:1.
- Starting System: Electric starter with auxiliary recoil.
- Transmission: 5-speed with reverse, Ultramatic® automatic V-belt.
- Drive System: On-Command® 2WD/4WD with differential lock.
- Suspension Front/Rear: Independent double wishbone / Swingarm.
- Brakes Front/Rear: Dual hydraulic disc / Sealed wet multi-disc.
- Tires: AT25 x 8-12 front, AT25 x 10-12 rear.
- Fuel Capacity: 4.0 gal (15.1 L).
- Dry Weight: 595 lb (270 kg).
Periodic Maintenance
Follow the maintenance schedule for optimal performance and longevity. Service intervals are based on hours of operation or mileage.
- Pre-Ride Inspection: Check tires, controls, lights, oil level, coolant, brakes.
- Every 100 mi / 1 month: Check air filter, drive chain slack/tension.
- Every 600 mi / 6 months: Change engine oil and filter. Check valve clearance, brake pads, CVT air filter.
- Every 1,200 mi / 12 months: Replace spark plug, clean fuel filter, inspect brake fluid, grease all fittings.
- Every 2 years: Replace brake fluid, coolant.
WARNING! Always use Yamaha Genuine Parts or equivalents. Improper maintenance can lead to component failure or accident.
Engine
Service procedures for the 421cc air-cooled engine, including top-end and bottom-end service.
- Engine Removal: Disconnect battery, drain coolant, remove exhaust, intake, electrical connectors, mounting bolts.
- Cylinder Head & Valves: Remove camshaft, valves; inspect for wear; adjust valve clearance to 0.10–0.15 mm (cold).
- Cylinder & Piston: Measure cylinder bore (standard 87.500–87.515 mm), piston clearance, ring end gap.
- Crankcase & Crankshaft: Split crankcase; inspect bearings, connecting rod big-end play.
- Reassembly: Use new gaskets and seals. Torque cylinder head bolts in sequence to 20 Nm (14.8 ft-lb).
CAUTION! Keep work area clean. Mark all parts and connectors during disassembly.
Cooling System
The liquid-cooled system maintains optimal engine temperature.
- Radiator: Inspect for leaks, damage, clogged fins. Clean with low-pressure air or water.
- Coolant: Use high-quality ethylene glycol antifreeze. Capacity: 1.59 L (1.68 US qt).
- Thermostat: Opens at 71–85°C (160–185°F). Test in heated water.
- Water Pump: Inspect impeller and seal for wear or leaks.
- Bleeding: After refill, run engine with radiator cap off until thermostat opens and coolant circulates.
Fuel System
Carburetor and fuel delivery system service.
- Carburetor Removal: Drain fuel, disconnect throttle and choke cables, fuel line, vent lines.
- Cleaning & Rebuild: Disassemble; clean all jets and passages with carb cleaner; replace gaskets and O-rings.
- Float Level: Adjust to 6.5 mm (0.26 in).
- Pilot Screw: Initial setting: 2-1/4 turns out from lightly seated.
- Fuel Pump: Test flow and pressure. Replace if defective.
- Fuel Filter: Replace annually or if clogged.
WARNING! Work in well-ventilated area. No smoking or open flames near fuel.
Drive Train
Ultramatic® transmission, drive shaft, front and rear differentials.
| Component | Service Procedure |
|---|
| CVT Drive Belt | Inspect for cracks/wear. Replace if width < 27.0 mm. Adjust belt deflection. |
| Primary/Secondary Clutch | Clean sheaves; inspect rollers, weights, spring for wear. |
| On-Command 4WD | Check engagement; inspect shift motor, actuator, wiring. |
| Front/Rear Differential | Drain and refill gear oil (SAE 80W-90). Capacity: 0.23 L each. |
| Drive Shaft & U-Joints | Lubricate splines and joints with grease. Check for play. |
Chassis
Frame, suspension, steering, and brakes.
- Front Suspension: Check A-arm bushings, ball joints, shock absorbers for leaks or damage.
- Rear Suspension: Inspect swingarm pivot bearings, shock linkage.
- Steering: Check for free play. Adjust if necessary. Grease steering stem bearings.
- Brakes: Measure pad thickness (replace if < 1.0 mm). Bleed hydraulic system. Adjust parking brake cable.
- Wheels & Tires: Check for damage, proper inflation (Front: 3.5 psi, Rear: 3.5 psi for standard terrain).
Electrical System
Battery, charging, starting, lighting, and ignition systems.
- Battery: 12V, 12Ah. Maintain specific gravity at 1.280. Keep terminals clean and tight.
- Charging System: Stator resistance: 0.36–0.48 Ω. Regulator/Rectifier output: 13.5–15.5 V at 5000 RPM.
- Starting System: Starter motor draw: < 90 A. Solenoid check for continuity.
- Ignition System: Spark plug gap: 0.6–0.7 mm. Ignition coil primary resistance: 0.56–0.84 Ω.
- Lighting & Switches: Test all lights, horn, switches, and indicators.
Troubleshooting
| Symptom | Possible Cause | Corrective Action |
|---|
| Engine won't start | Weak battery, faulty ignition, fuel issue | Check battery voltage, spark, fuel delivery. Clean carburetor. |
| Poor performance/loss of power | Clogged air filter, CVT issues, restricted exhaust | Replace air filter, inspect CVT belt/clutches, check spark arrestor. |
| Overheating | Low coolant, clogged radiator, faulty thermostat | Check coolant level and condition, clean radiator fins, test thermostat. |
| 4WD not engaging | Faulty actuator, switch, wiring | Test 4WD switch and motor. Check for power at connector. |
| Electrical failure (no lights) | Blown fuse, bad ground, faulty switch | Check main 30A fuse and individual fuses. Inspect ground connections. |
| Abnormal noise from drivetrain | Worn U-joints, differential issues, bad bearings | Inspect drive shaft, differential gear oil, wheel bearings. |
Note: Use a multimeter and service manual wiring diagrams for accurate electrical diagnosis.
Wiring Diagrams
Refer to the full-color wiring diagrams at the back of the physical manual or in the digital PDF for complete electrical system schematics, connector views, and component locations. Diagrams include:
- Main Harness
- Lighting System
- Starting & Charging System
- Ignition & CDI System
- 4WD System Control
- Gauge Cluster
CAUTION! Always disconnect the battery negative terminal before performing electrical work to prevent shorts or ECU damage.
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