Grizzly 660 Service Manual

The Grizzly 660 is a 4x4 all-terrain vehicle (ATV) featuring a 660cc liquid-cooled, four-stroke engine, Ultramatic automatic transmission with engine braking, On-Command 2WD/4WD with differential lock, independent double wishbone front suspension, and a fully sealed wet brake system. This service manual provides comprehensive information for maintenance, troubleshooting, repair, and specifications. Below are key sections covering safety, periodic maintenance, engine service, chassis, electrical systems, and troubleshooting procedures.

General Information & Safety

This manual is intended for qualified service technicians. Always follow safety procedures to prevent injury or damage.

Item	Description
Model Identification	YFM660FW (Grizzly 660 4x4)
Manual Purpose	Provide service, maintenance, and repair information
Safety Symbols	WARNING, CAUTION, NOTE indicate hazard levels
Tool Requirements	Standard mechanic tools, Yamaha special tools as noted
Parts Reference	Use genuine Yamaha parts for repair and replacement

WARNING! Always disconnect battery before servicing electrical components. Support ATV securely on a stand before working underneath.

Periodic Maintenance

Regular maintenance ensures optimal performance and longevity. Follow the maintenance schedule based on operating hours or mileage.

1. Pre-ride Inspection: Check tires, brakes, lights, controls, and fluid levels.
2. Engine Oil & Filter: Change every 100 hours or 6 months; use recommended 10W-30 or 10W-40.
3. Air Filter: Clean foam element every 20-50 hours; replace if damaged.
4. Drive Chain: Clean, lubricate, and adjust tension every 20 hours.
5. Front & Rear Gearcase Oil: Check level and change per schedule.
6. Brake Fluid: Inspect reservoir level; change fluid every 2 years.
7. Spark Plug: Clean and gap every 100 hours; replace as needed.
8. Valve Clearance: Inspect and adjust every 200 hours.

CAUTION! Use only specified lubricants and fluids. Torque all fasteners to specified values.

Engine Service

The 660cc engine is a liquid-cooled, SOHC, 4-valve design with a Mikuni BSR42 carburetor.

• Cylinder Head & Valves: Procedures for removal, valve adjustment (IN: 0.10–0.15 mm, EX: 0.15–0.20 mm), and reassembly.
• Cylinder & Piston: Inspection for wear, piston ring end gap, and cylinder honing.
• Crankcase & Crankshaft: Splitting crankcase, inspecting bearings, and connecting rod play.
• Clutch: Servicing the Ultramatic centrifugal clutch and belt.
• Cooling System: Radiator cleaning, thermostat check, coolant replacement (50/50 ethylene glycol).
• Lubrication System: Oil pump inspection and pressure relief valve.

Note: Always replace gaskets and seals during reassembly. Refer to torque specifications in the manual.

Chassis & Suspension

Frame, suspension components, steering, and wheels.

1. Frame Inspection: Check for cracks or damage, especially at weld points.
2. Front Suspension: Double wishbone with 6.7 in travel; service shock absorbers and A-arm bushings.
3. Rear Suspension: Swingarm with 7.5 in travel; check pivot bearings and shock preload.
4. Steering System: Handlebar alignment, steering shaft bearing adjustment.
5. Wheels & Tires: Tire pressure (Front: 3.5 psi / 24 kPa, Rear: 3.5 psi / 24 kPa); wheel bearing inspection.

Tip: Lubricate all suspension pivot points with grease during service.

Electrical System

12V DC system with battery, starter, charging system, lighting, and switches.

Component	Specification/Test
Battery	YTZ10S (12V 8.6Ah); voltage: 12.8V fully charged
Starter Motor	Brush length min: 8.5 mm; commutator undercut: 0.5–0.8 mm
Charging System	AC magneto; regulated voltage: 14V at 5000 rpm
Headlight	12V 30/30W (halogen)
Fuses	Main: 30A; Headlight: 15A; Signal: 10A
CDI Unit	Check resistance values per manual; replace if out of spec

WARNING! Disconnect battery negative terminal first. Avoid short circuits.

Fuel & Exhaust System

Fuel tank capacity: 4.8 gal (18.2 L). Carburetor settings and exhaust service.

1. Carburetor: Pilot screw initial setting: 2-1/4 turns out; float height: 13.5 mm.
2. Throttle Cable: Adjust free play to 3–5 mm.
3. Fuel Valve: Inspect for leaks; clean sediment cup.
4. Exhaust System: Remove heat shield; check for leaks at header pipe.
5. Air Induction System: Check AIS hoses and valves for proper operation.

CAUTION! Work in well-ventilated area. No smoking near fuel system.

Drive System

On-Command 2WD/4WD with differential lock. Ultramatic automatic transmission with high/low range and reverse.

• Front Differential: Oil capacity: 0.26 US qt (0.25 L); check for seal leaks.
• Rear Gearcase: Oil capacity: 0.42 US qt (0.40 L); drain and refill per schedule.
• Drive Shafts: Inspect CV joints and boots for damage.
• 4WD Actuator: Test engagement; check wiring and switch operation.
• Differential Lock: Test engagement lever and cable adjustment.

Note: Use API GL-4 Hypoid gear oil SAE 80W-90 for differentials and gearcase.

Brake System

Dual hydraulic disc brakes front, sealed wet multi-disc brake rear.

1. Front Brakes: Check pad thickness (min: 0.12 in / 3.0 mm); bleed system if spongy.
2. Rear Brake: Inspect brake shoes; adjust lever free play (10–20 mm).
3. Brake Fluid: Use DOT 4; flush every 2 years.
4. Parking Brake: Adjust cable for proper engagement.

WARNING! Brake fluid is corrosive. Avoid contact with paint and skin.

Specifications

• Engine Type: Liquid-cooled, 4-stroke, SOHC, 4-valve
• Displacement: 660 cc
• Bore x Stroke: 102.0 mm x 80.5 mm
• Compression Ratio: 9.2:1
• Fuel System: Mikuni BSR42 carburetor
• Starting System: Electric starter with auxiliary recoil
• Transmission: Ultramatic V-belt automatic with H/L/R
• Drive System: On-Command 2WD/4WD with diff lock
• Suspension Front/Rear: Double wishbone / Swingarm
• Brakes Front/Rear: Dual hydraulic disc / Sealed wet multi-disc
• Tires Front/Rear: AT25 x 8-12 / AT25 x 10-12
• Dimensions (LxWxH): 81.9 in x 46.5 in x 48.4 in
• Dry Weight: 602 lb (273 kg)
• Fuel Capacity: 4.8 gal (18.2 L)

Troubleshooting

Symptom	Possible Cause	Corrective Action
Engine does not start	Weak battery, faulty spark, fuel issue	Check battery voltage, spark plug, fuel flow to carburetor.
Engine stalls or runs rough	Clogged fuel filter, dirty carburetor, bad plug	Clean fuel system, adjust carburetor, replace spark plug.
4WD does not engage	Actuator failure, switch problem, wiring	Test actuator motor, check switch and connections.
Excessive vibration	Unbalanced wheels, worn drive shaft CV joint	Balance tires, inspect CV joints and boots.
Brakes dragging or weak	Contaminated pads, air in lines, worn shoes	Clean or replace pads, bleed brakes, adjust rear brake.
Electrical failure (no lights)	Blown fuse, bad ground, faulty switch	Check fuses, ground connections, and switch continuity.

Reset: For ECU/electronic issues, disconnect battery for 10 minutes to reset.

Service: For technical support, contact Yamaha Motor Corporation or authorized dealer.

Wiring Diagrams

Refer to the separate fold-out wiring diagram sheet included with this manual for complete electrical schematics, connector locations, and wire color codes for the entire Grizzly 660 system.

Note: Diagrams are specific to model year and region. Use the correct diagram for your VIN.