Stihl 066 Shop Manual

The Stihl 066 Shop Manual is a comprehensive service and repair guide for the Stihl 066 professional chainsaw. It covers engine specifications, fuel and oil systems, ignition, carburetor, starting system, clutch and chain brake, chain and bar, troubleshooting, maintenance procedures, and safety precautions. Below are key sections for specifications, maintenance, repair, troubleshooting, and parts information.

Specifications

Key technical data for the Stihl 066 chainsaw.

Feature	Description
Engine Type	2-stroke, single cylinder, air-cooled
Displacement	91.6 cc (5.59 cu. in.)
Power Output	6.4 kW (8.7 hp)
Fuel Tank Capacity	825 ml (27.9 fl. oz.)
Oil Tank Capacity	410 ml (13.9 fl. oz.)
Idle Speed	2,800 rpm
Max Engine Speed	13,500 rpm
Weight (without cutting equipment)	7.9 kg (17.4 lbs)
Guide Bar Length Range	50 cm (20") to 105 cm (41")
Chain Pitch	3/8" or .404"

Safety Precautions

Essential safety guidelines for operating and servicing the Stihl 066 chainsaw.

1. Always wear protective equipment: helmet, goggles, gloves, chainsaw chaps, and hearing protection.
2. Ensure chainsaw is turned off and spark plug disconnected before performing any maintenance.
3. Use only Stihl-approved replacement parts and accessories.
4. Work in a well-ventilated area when handling fuel or performing engine repairs.

WARNING! Failure to follow safety procedures can result in serious injury or death. Always refer to the operator's manual before use.

Maintenance Schedule

Recommended maintenance intervals for optimal performance and longevity.

1. Daily: Check chain tension, sharpness, and lubrication; inspect for loose fasteners.
2. Weekly: Clean air filter, check spark plug, inspect fuel filter and lines.
3. Monthly: Clean cooling fins, check clutch drum and sprocket, inspect anti-vibration elements.
4. Annually: Replace fuel filter, inspect ignition system, check cylinder and piston for wear.

CAUTION! Use only Stihl high-performance 2-stroke engine oil mixed at 50:1 ratio with unleaded gasoline (min. 89 octane).

Engine Repair

• Cylinder & Piston: Inspection, removal, and installation procedures.
• Crankshaft & Bearings: Disassembly, bearing replacement, reassembly.
• Carburetor Adjustment: Setting idle (L), high speed (H), and idle speed screws.
• Muffler: Cleaning and spark arrestor maintenance.
• Decompression Valve: Testing and replacement if faulty.
• Supported Tools: Stihl special tools for flywheel puller, piston stop, etc.
• Torque Specifications: Cylinder bolts: 10 Nm; Spark plug: 25 Nm; Clutch: 40 Nm.
• Operating Temp: Normal operating range: 0°C to 40°C (32°F to 104°F).

Fuel System

Components: Fuel tank, filter, lines, carburetor (Walbro or Zama), fuel pump.

Carburetor: Adjust L (low speed) and H (high speed) screws; set idle speed with T screw.

Fuel Filter: Replace annually or if clogged. Fuel Lines: Inspect for cracks; replace if leaking. Fuel Pump: Test diaphragm; replace if engine runs lean. Troubleshooting: Engine stalls at idle (adjust L screw); lacks power (check H screw, fuel filter).

Ignition System

Components: Spark plug (Bosch WSR6F or equivalent), ignition module, flywheel, stop switch.

1. Turn off chainsaw and disconnect spark plug before servicing.
2. Check spark plug gap: 0.5 mm (0.020 in.).
3. Test ignition module with multimeter (primary resistance: 0.5-1.5 Ω).

Tip: Ensure flywheel key is not sheared; timing must be correct for proper ignition.

Chain & Bar Assembly

Supports .404" and 3/8" pitch chains; bar lengths 50-105 cm.

1. Install bar: Place bar onto studs, align chain with sprocket, adjust tension.
2. Tension chain: Loosen nuts, adjust tensioning screw until chain snaps back when lifted.
3. Sharpen chain: Use round file matching chain pitch; maintain 30° cutting angle.
4. Lubricate: Ensure oiler is functioning; use Stihl chain oil.
5. Inspect: Check for worn drive links, damaged bar rails, and sprocket wear.
6. Replace: Bar if rails are uneven; sprocket if worn; chain if stretched or damaged.
7. Depth gauges: File to 0.65 mm (0.025 in.) below cutter top plate.
8. Storage: Clean and oil bar and chain to prevent rust.

WARNING! Always wear gloves when handling chain. Ensure chain brake is functional before use.

Clutch & Chain Brake

Clutch: Centrifugal type; engages at ~2,800 rpm. Chain Brake: Manual/inertia activated; stops chain within 0.12 seconds.

Care & Cleaning

Clean exterior with damp cloth; remove debris from cooling fins and air filter. Store in dry place.

CAUTION! Do not use high-pressure water; avoid solvents on plastic parts.

Regulatory Information

EPA certified for emissions; meets ANSI B175.1 safety standards. Copyright © Stihl Incorporated; all trademarks property of Stihl. For support, visit www.stihlusa.com or contact 1-800-467-8445.

Troubleshooting

Symptom	Possible Cause	Corrective Action
Engine will not start	No spark, flooded, fuel issue	Check spark plug, ignition; dry plug; clean carburetor, replace fuel filter.
Engine runs but dies	Clogged filter, carburetor adjustment	Clean air/fuel filters; adjust L and H screws.
Chain does not turn	Clutch worn, chain brake engaged	Inspect clutch shoes; disengage chain brake.
Excessive vibration	Loose parts, unbalanced chain	Tighten all fasteners; balance chain.
Overheating	Dirty cooling fins, lean mixture	Clean fins; adjust carburetor richer.

Reset: Adjust carburetor to factory settings: L - 1 turn open, H - 1 turn open.

Service: 1-800-467-8445; www.stihlusa.com