2007 Yamaha Grizzly 450 Service Manual

The 2007 Yamaha Grizzly 450 is a 4x4 all-terrain vehicle (ATV) powered by a 421cc, 4-stroke, liquid-cooled, SOHC engine with Ultramatic automatic transmission, On-Command 2WD/4WD with differential lock, independent front and rear suspension, and electric start. This manual provides comprehensive service, maintenance, and repair information for owners and technicians. Below are key sections covering specifications, periodic maintenance, engine service, chassis, electrical, troubleshooting, and warranty.

1. General Information 2. Specifications 3. Periodic Maintenance 4. Engine 5. Chassis 6. Electrical System 7. Troubleshooting 8. Lubrication & Fluids 9. Storage & Winterization 10. Safety Precautions 11. Warranty & Support

General Information

This manual covers the 2007 Yamaha Grizzly 450 (YFM45FAT). Includes identification numbers (VIN, engine), model features, and general safety information for service operations.

Item	Description
Model	YFM45FAT (Grizzly 450 4x4 Auto)
Vehicle Identification Number (VIN)	Located on frame steering head
Engine Serial Number	Stamped on right side of crankcase
Recommended Fuel	Unleaded gasoline (87 octane or higher)
Oil Type	Yamalube 4 (10W-30) or equivalent API SG/SH/SJ
Coolant	Yamaha Coolant or high-quality ethylene glycol antifreeze
Battery	12V, 12Ah (YTZ7S)
Tire Pressure (Front/Rear)	3.5 psi (24 kPa) / 3.5 psi (24 kPa)
Load Capacity	198 lbs (90 kg) rider + 132 lbs (60 kg) cargo
Towing Capacity	Not recommended for towing

Specifications

Engine Type: 4-stroke, liquid-cooled, SOHC, 4-valve
Displacement: 421cc
Bore x Stroke: 83.0 mm x 77.8 mm
Compression Ratio: 9.5:1
Starting System: Electric starter with auxiliary recoil
Transmission: Yamaha Ultramatic automatic V-belt with all-wheel engine braking
Drive System: Yamaha On-Command 2WD/4WD with differential lock
Suspension Front: Independent double wishbone, 7.1 in travel
Suspension Rear: Independent double wishbone, 8.7 in travel
Brakes Front: Dual hydraulic disc
Brakes Rear: Sealed, oil-bathed multi-disc
Tires Front/Rear: AT25 x 8-12 / AT25 x 10-12
Fuel Capacity: 4.0 gal (15 L)
Dry Weight: 595 lbs (270 kg)
Overall Length/Width/Height: 81.5 in / 46.1 in / 48.4 in

Periodic Maintenance

Follow maintenance schedule to ensure optimal performance and longevity.

Pre-ride Inspection: Check tires, brakes, lights, controls, fluid levels.
Every 100 mi / 1 month: Check engine oil, coolant, brake fluid, drive chain slack and lubrication.
Every 500 mi / 6 months: Change engine oil and filter, inspect air filter, check valve clearance, inspect brake pads, lubricate all pivots and cables.
Every 1,000 mi / 12 months: Change coolant, inspect spark plug, replace air filter if dirty, check wheel bearings, inspect suspension components.
Every 2,000 mi: Replace spark plug, inspect fuel line, clean carburetor, check electrical connections.

WARNING! Always perform maintenance with engine off and cool. Use proper tools and safety equipment.

Engine

Service procedures for engine removal, disassembly, inspection, and reassembly.

Cylinder Head & Valves: Removal, decarbonizing, valve lapping, clearance adjustment (intake 0.10–0.15 mm, exhaust 0.15–0.20 mm).

Cylinder & Piston: Inspection for wear, scoring; piston ring end gap (0.15–0.30 mm).

Crankcase & Crankshaft: Disassembly, connecting rod side clearance (0.35–0.65 mm), main bearing inspection.

Lubrication System: Oil pump inspection, pressure relief valve, oil strainer cleaning.

Cooling System: Radiator cleaning, thermostat check (opens at 71–85°C), water pump impeller inspection.

Fuel System: Carburetor (Mikuni BSR36) adjustment, float level (16.5 mm), pilot screw setting (2-1/4 turns out).

Exhaust System: Removal, cleaning of spark arrestor.

Chassis

Frame, suspension, steering, brakes, wheels, and final drive service.

Frame: Inspection for cracks, damage; tightening of all bolts to specified torque.
Front Suspension: A-arm removal, shock absorber service (preload adjustment), ball joint inspection.
Rear Suspension: Similar to front; check for worn bushings.
Steering: Handlebar alignment, steering stem bearing adjustment and lubrication.
Brakes: Pad replacement (min thickness 0.5 mm), disc inspection (min thickness 3.0 mm), bleeding procedure.
Wheels & Tires: Tire replacement, wheel bearing inspection and replacement.
Final Drive: Drive chain adjustment (1.2–1.6 in slack), lubrication; front differential oil change (every 500 mi).

Tip: Use a torque wrench for all critical fasteners; refer to torque specifications in manual.

Electrical System

Battery, charging system, ignition, lighting, switches, and wiring diagram.

Component	Specification/Test
Battery	Voltage: 12.8V fully charged; load test: 9.6V min @ 68A for 10 sec
Charging System	Stator coil resistance: 0.21–0.31 Ω; voltage: 13.5–15.5V @ 5000 rpm
Ignition System	Spark plug: NGK CR7E; gap: 0.6–0.7 mm; ignition coil resistance: primary 0.16–0.24 Ω, secondary 6.5–9.8 kΩ
Starter Motor	Brush length min: 6.5 mm; commutator diameter min: 22 mm
Lighting	Headlight: 12V 30/30W; brake/tail: 12V 21/5W
Fuses	Main: 30A; Headlight: 10A; Signal: 10A

CAUTION! Disconnect battery negative terminal before performing electrical work to prevent short circuits.

Troubleshooting

Symptom	Possible Cause	Corrective Action
Engine does not start	Weak battery, faulty spark plug, clogged fuel filter, carburetor issue	Charge/replace battery; check spark; clean fuel system; inspect carburetor.
Engine stalls or runs rough	Dirty air filter, incorrect idle speed, water in fuel, valve clearance	Clean/replace air filter; adjust idle (1400±100 rpm); drain fuel; adjust valves.
Overheating	Low coolant, clogged radiator, faulty thermostat, low oil	Fill coolant; clean radiator; replace thermostat; check oil level.
Poor performance/loss of power	Clogged exhaust spark arrestor, worn drive belt, compression loss	Clean spark arrestor; inspect drive belt; check compression (standard: 128 psi).
Electrical failure (no lights)	Blown fuse, bad battery connection, faulty switch	Check/replace fuses; clean terminals; test switch continuity.
Transmission slipping	Worn drive belt, improper belt alignment, worn sheaves	Inspect belt for wear/cracks; align primary/secondary sheaves.
4WD not engaging	Faulty On-Command switch, wiring issue, differential problem	Test switch; check wiring; inspect front differential actuator.

Reset: Disconnect battery for 10 minutes to reset ECU if experiencing electronic issues.

Lubrication & Fluids

Recommended fluids and capacities.

Engine Oil: SAE 10W-30 (API SG/SH/SJ), capacity 2.6 qt (2.5 L) with filter change.
Oil Filter: Yamaha part #5GH-13440-30-00 or equivalent.
Coolant: High-quality ethylene glycol antifreeze (50/50 mix), capacity 1.6 qt (1.5 L).
Front Differential Oil: SAE 80W-90 GL-5 gear oil, capacity 0.26 qt (0.25 L).
Brake Fluid: DOT 4.
Grease Points: Suspension pivots, steering stem, brake pedal, drive chain (Yamaha Chain Lube).

WARNING! Dispose of used oil and fluids properly according to local regulations.

Storage & Winterization

Proper procedures for storing ATV for extended periods.

Clean ATV thoroughly.
Change engine oil and filter.
Fill fuel tank and add fuel stabilizer; run engine for 5 minutes.
Remove spark plug, add teaspoon of oil into cylinder, crank engine, reinstall plug.
Disconnect battery, clean terminals, store in cool, dry place on a maintainer.
Inflate tires to recommended pressure; store on blocks to relieve weight.
Cover ATV with breathable cover.

CAUTION! Do not store with fuel in carburetor without stabilizer to prevent varnish buildup.

Safety Precautions

Essential safety information for servicing the Grizzly 450.

Always work in a well-ventilated area.
Use jack stands; never rely solely on a hydraulic jack.
Wear safety glasses, gloves, and appropriate clothing.
Keep away from moving parts when engine is running.
Ensure ATV is securely supported before working underneath.
Keep fire extinguisher nearby when working with fuel or battery.
Follow torque specifications; do not overtighten fasteners.

WARNING! Gasoline is highly flammable. No smoking or open flames in service area.

Warranty & Support

Yamaha Motor Corporation, U.S.A. provides a limited warranty. See your Yamaha dealer for details. For technical support, contact Yamaha Customer Relations at 1-800-962-7926 or visit www.yamahamotorsports.com. Always use genuine Yamaha parts for optimum performance and warranty compliance.

Service Note: This manual is intended for use by qualified technicians. Incorrect repairs can lead to unsafe operation. Dealer service is recommended for major repairs.