2007 Yamaha Grizzly 450 Repair Manual

The 2007 Yamaha Grizzly 450 is a four-wheel-drive all-terrain vehicle (ATV) featuring a 421cc liquid-cooled, SOHC, 4-stroke engine, Ultramatic automatic transmission with engine braking, On-Command 2WD/4WD with differential lock, independent double-wishbone front suspension, and a swingarm rear suspension. This manual provides comprehensive repair, maintenance, and troubleshooting procedures for owners and technicians. Below are key sections covering safety, specifications, periodic maintenance, engine service, chassis, electrical, and troubleshooting.

1. General Information & Safety 2. Specifications 3. Periodic Maintenance & Lubrication 4. Engine 5. Fuel System & Carburetor 6. Chassis & Drive System 7. Electrical System 8. Troubleshooting 9. Wiring Diagrams 10. Appendix: Torque Specifications

General Information & Safety

This manual is intended for persons with basic mechanical skills and tools. Always prioritize safety when performing repairs.

Safety SymbolMeaning
WARNINGIndicates a potential hazard that could result in serious injury or death.
CAUTIONIndicates a potential hazard that could result in minor injury or product damage.
NOTEProvides helpful information and tips for proper procedure.

WARNING! Always disconnect the battery negative (-) cable before servicing electrical components. Allow the engine and exhaust system to cool completely before working near them. Use proper lifting and support equipment.

Specifications

Periodic Maintenance & Lubrication

Follow the maintenance schedule to ensure optimal performance and longevity.

  1. Pre-ride Inspection: Check tires, controls, lights, oil level, and for fluid leaks.
  2. Engine Oil & Filter: Change every 100 hours or 6 months, whichever comes first. Use Yamalube 4 (10W-30) or equivalent.
  3. Air Filter: Clean every 20-40 hours; replace if damaged. Use foam air filter oil.
  4. Drive Chain: Clean and lubricate every 500 miles. Adjust slack to 1.2-1.6 in.
  5. Front & Rear Gearcase Oil: Check level; change every 2 years or 200 hours.
  6. Brake Fluid: Check reservoir level; replace fluid every 2 years. Use DOT 4.
  7. Spark Plug: NGK CR7E. Clean and adjust gap to 0.028-0.031 in every 100 hours.

CAUTION! Do not over-tighten the oil drain plug or filter cap. Use a torque wrench.

Engine

Procedures for top-end service, cylinder head, valve adjustment, and bottom-end inspection.

Valve Clearance Adjustment: Perform cold. Intake: 0.10-0.15 mm (0.004-0.006 in). Exhaust: 0.15-0.20 mm (0.006-0.008 in).

Cylinder Head Removal:

  1. Drain coolant and remove radiator.
  2. Remove camshaft cover, cam chain tensioner, and camshaft.
  3. Remove cylinder head bolts in crisscross pattern.
  4. Inspect head for warpage (max 0.03 mm).

Piston & Cylinder: Standard piston diameter: 82.955-82.970 mm. Service limits provided in manual.

Fuel System & Carburetor

Mikuni BSR42 carburetor service and adjustment.

  1. Carburetor Removal: Disconnect fuel line, throttle cables, and vent hoses.
  2. Cleaning: Disassemble and clean all jets and passages with carb cleaner and compressed air.
  3. Pilot Screw Setting: Initial setting: 2-1/4 turns out from lightly seated.
  4. Float Height: 13.0-15.0 mm (0.51-0.59 in).
  5. Fuel Pump: Test operation; replace if not delivering fuel.

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

Chassis & Drive System

Front and rear suspension, brakes, and On-Command 4WD system service.

Front A-Arm & Shock Removal: Support ATV, remove wheel, disconnect shock lower mount, remove A-arm pivot bolts.

Brake Pad Replacement: Remove caliper, push piston back, replace pads, reinstall.

On-Command System Troubleshooting: If 4WD or diff lock does not engage, check vacuum lines, solenoid, and actuator. Refer to specific test procedures.

WARNING! Always bleed brakes after opening the hydraulic system. Do not reuse brake fluid.

Electrical System

Battery, charging system, starter, and lighting.

ComponentSpecification/Test
BatteryYTZ7S (12V, 6.3Ah). Charging voltage: 14.1-14.9V @ 5000 rpm.
Stator Coil Resistance0.36-0.48 Ω (White-White) @ 20°C (68°F).
Regulator/RectifierCheck diode continuity. Replace if faulty.
Starter RelayClick test; check continuity across heavy terminals when energized.

CAUTION! Disconnect battery before testing. Use a multimeter for accurate readings.

Troubleshooting

SymptomPossible CauseCorrective Action
Engine does not startWeak battery, faulty spark, fuel issueCheck battery voltage, spark plug, fuel flow to carb.
Engine starts but diesClogged pilot jet, vacuum leakClean carburetor, inspect intake boot for cracks.
Poor performance/loss of powerDirty air filter, restricted exhaust, worn clutchService air filter, check exhaust spark arrestor, inspect drive belt.
4WD not engagingVacuum line leak, faulty actuatorInspect all vacuum lines, test 4WD solenoid.
Electrical accessories not workingBlown fuse, bad connectionCheck main 30A fuse and individual circuit fuses.
OverheatingLow coolant, clogged radiator, bad thermostatCheck coolant level and condition, clean radiator fins.

Wiring Diagrams

Refer to the full-color, system-specific wiring diagrams included in the back of the physical manual for complete electrical troubleshooting. Diagrams cover:

NOTE: Wire colors are abbreviated: R=Red, B=Black, W=White, G=Green, Y=Yellow, L=Blue, Br=Brown, O=Orange.

Appendix: Torque Specifications

Critical fasteners and their torque values (ft-lb / Nm).

FastenerTorque
Cylinder Head Bolts (8mm)20 ft-lb / 27 Nm
Spark Plug13 ft-lb / 18 Nm
Engine Oil Drain Plug20 ft-lb / 27 Nm
Front Wheel Axle Nut65 ft-lb / 88 Nm
Rear Wheel Axle Nut87 ft-lb / 118 Nm
Front Sprocket / Drive Flange Nut65 ft-lb / 88 Nm
Shock Absorber Mounting Nuts (Upper/Lower)29 ft-lb / 39 Nm

WARNING! Always use a calibrated torque wrench. Do not guess torque values.

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