Stihl 012 Service Manual

The Stihl 012 is a lightweight, professional-grade chainsaw designed for demanding cutting tasks. This service manual provides comprehensive information for maintenance, troubleshooting, and repair of the Stihl 012 chainsaw, including engine specifications, fuel system, ignition system, chain brake, lubrication system, and safety procedures. Below are key sections covering safety, specifications, maintenance procedures, troubleshooting, and parts information.

Features at a Glance

Key components: Single-cylinder two-stroke engine, anti-vibration system, chain brake, automatic oiler, manual oil pump, decompression valve, and electronic ignition.

Feature	Description
Engine Type	Single cylinder, two-stroke, air-cooled
Displacement	31.8 cc (1.94 cu. in.)
Power Output	1.6 kW (2.1 hp)
Fuel Tank Capacity	0.25 L (0.066 US gal)
Oil Tank Capacity	0.20 L (0.053 US gal)
Guide Bar Lengths	12" to 16" (30 cm to 40 cm)
Chain Pitch	3/8" PMM or 0.325"
Ignition System	Electronic, breakerless
Weight (powerhead)	Approx. 4.2 kg (9.3 lbs)
Anti-Vibration System	Yes

Safety Information

Always follow safety procedures to prevent serious injury or death.

1. Personal Protective Equipment (PPE): Always wear chainsaw chaps, gloves, eye protection, hearing protection, and sturdy boots.
2. Pre-Operation Check: Inspect chain tension, sharpness, and lubrication. Check for loose fasteners and fuel leaks.
3. Starting & Operation: Start on ground or solid surface. Maintain secure footing and grip. Keep bystanders at a safe distance.
4. Chain Brake: Test function before each use. Engage chain brake when carrying saw or not actively cutting.

WARNING! Never operate a chainsaw without proper training and safety gear. Kickback can occur suddenly and cause loss of control.

Specifications

• Model: Stihl 012
• Engine: 31.8 cc two-stroke, single cylinder
• Bore x Stroke: 38 mm x 28 mm
• Powerhead Weight: 4.2 kg (9.3 lbs)
• Fuel Mix Ratio: 50:1 (Stihl HP Ultra or equivalent ISO-L-EGD certified oil)
• Idle Speed: 2,800 RPM
• Maximum Power Speed: 9,500 RPM
• Spark Plug: Bosch WSR 6 F or equivalent, gap 0.5 mm (0.020")
• Chain Oil: Stihl chainsaw oil or equivalent biodegradable oil
• Sound Pressure Level: Approx. 106 dB(A)
• Vibration Level: Left/Right: 4.5 m/s², Front/Rear: 2.5 m/s²

Maintenance Schedule

Regular maintenance ensures optimal performance and longevity.

Interval	Task
Before each use	Check chain tension, sharpness, and lubrication. Inspect for damage/loose parts.
Every 5 hours	Clean air filter. Check spark plug condition.
Every 20 hours	Clean spark arrestor screen (if equipped). Check fuel filter.
Every 50 hours	Replace fuel filter. Clean cooling fins. Check carburetor adjustment.
Every 100 hours	Replace spark plug. Clean exhaust port and muffler. Inspect piston through exhaust port.
Annually	Replace air filter. Check all rubber mounts and AV buffers.

Note: Service intervals may vary based on operating conditions.

Engine Service

Procedures for cylinder, piston, crankshaft, and bearings.

1. Cylinder & Piston Inspection: Remove muffler to inspect piston and cylinder for scoring, wear, or carbon buildup.
2. Compression Test: Should be a minimum of 120 psi (8.3 bar). Low compression indicates worn piston rings or cylinder.
3. Crankshaft Seals: Check for leaks which can cause lean running condition. Replace if oil residue is present outside seals.
4. Decompression Valve: Clean and ensure it seals properly. Replace if leaking.

Torque Specifications: Cylinder bolts: 10 Nm (88 in-lb). Spark plug: 25 Nm (18 ft-lb).

Fuel System

Carburetor adjustment, fuel lines, and filter replacement.

1. Fuel Mix: Use fresh 89+ octane gasoline mixed 50:1 with Stihl HP Ultra oil.
2. Carburetor Adjustment (Standard): Initial settings: L screw - 1 turn open, H screw - 1 turn open. Fine-tune for smooth acceleration and no four-stroking at full throttle.
3. Fuel Filter: Replace by disconnecting fuel line and pulling filter from tank. Install new filter and reconnect line.
4. Fuel Lines: Inspect for cracks or hardening. Replace if deteriorated.
5. Carburetor Diaphragms: Check for stiffness or holes. Replace carburetor kit if necessary.

WARNING! Never run engine without proper fuel/oil mixture. This will cause engine seizure.

Ignition System

Spark plug, ignition module, and stop switch testing.

1. Spark Plug: Use Bosch WSR 6 F or Champion RCJ 6Y. Gap to 0.5 mm (0.020"). Replace if electrode is worn or insulator is cracked.
2. Ignition Module (Coil): Air gap should be 0.3 mm (0.012"). Check for spark with tester. Replace module if no spark with proper gap.
3. Stop Switch: Test continuity. Should be open circuit when switch is off, closed when on.
4. Wiring: Inspect for damaged insulation or broken wires, especially where they pass through grommets.

Chain & Bar Maintenance

Sharpening, tensioning, and bar care.

1. Chain Sharpening: Use correct round file size (typically 4.0 mm for 3/8" PMM). Maintain 30° top plate cutting angle and 10° down angle. File all cutters to equal length.
2. Chain Tension: Adjust so chain snaps back when pulled from bar rail. Tighten bar nuts after adjustment.
3. Bar Maintenance: Flip bar regularly for even wear. Clean bar groove and oil holes. Dress bar rails with flat file if burred.
4. Sprocket: Inspect drive sprocket for wear. Replace if teeth are hooked or worn excessively.

Tip: A sharp chain reduces operator fatigue and improves cutting efficiency.

Lubrication System

Automatic and manual oiler service.

1. Oil Pump Output Check: Run saw at full throttle pointed at light surface. Should throw a line of oil.
2. Oil Pump Adjustment: Screw on bottom of saw controls output. Turn clockwise to increase, counterclockwise to decrease.
3. Oil Lines: Inspect pickup line in tank and delivery line to bar. Replace if cracked or leaking.
4. Oil Filter: Clean screen inside oil tank.
5. Manual Oil Pump (if equipped): Press plunger to deliver extra oil for difficult cuts.

Troubleshooting

Symptom	Possible Cause	Corrective Action
Engine will not start	No spark, flooded, fuel issues	Check spark, choke setting. Dry plug if flooded. Check fuel filter/lines.
Engine starts then dies	Clogged fuel filter, carb adjustment	Replace fuel filter. Adjust L screw. Check tank vent.
Lacks power at full throttle	Clogged air filter, spark arrestor, carb H setting	Clean/replace air filter. Clean spark arrestor. Adjust H screw.
Chain does not oil	Empty oil tank, clogged oil holes, faulty pump	Fill tank. Clean bar oil holes. Check oil lines and pump.
Excessive vibration	Loose components, unbalanced chain, worn AV mounts	Tighten all fasteners. Balance chain. Replace AV buffers.
Chain brake does not engage	Dirty mechanism, broken spring, worn band	Clean brake mechanism. Replace spring or brake band.

Note: For complex repairs, consult a Stihl authorized service dealer.

Parts Diagram & List

Refer to official Stihl 012 IPL (Illustrated Parts List) for complete breakdown. Key assembly groups:

1. Cylinder & Piston Assembly
2. Crankshaft & Crankcase
3. Carburetor & Air Filter Assembly
4. Ignition System & Flywheel
5. Clutch, Sprocket & Chain Brake
6. Oil Pump & Tank
7. Handle & Anti-Vibration System
8. Guide Bar & Chain

Ordering Parts: Use Stihl part numbers from IPL. Contact an authorized Stihl dealer for genuine parts.

Service Support: For technical assistance, contact Stihl USA at 1-800-467-8445 or visit www.stihlusa.com.