STIHL 018 Chainsaw Repair Manual

The STIHL 018 is a lightweight, professional-grade chainsaw featuring a single-cylinder, two-stroke engine with electronic ignition, automatic oiling system, anti-vibration handles, and a quick-stop chain brake. This repair manual covers safety procedures, technical specifications, troubleshooting, maintenance, and step-by-step repair instructions for engine, fuel system, ignition, chain drive, and controls. Below are key sections for safe operation, features, maintenance, troubleshooting, and repair procedures.

1. Safety Precautions 2. Specifications & Features 3. Maintenance Schedule 4. Troubleshooting Guide 5. Engine Repair 6. Fuel System 7. Ignition System 8. Chain & Bar Assembly 9. Controls & Safety Devices 10. Parts List & Diagrams 11. Warranty & Support

Safety Precautions

Always wear protective gear: safety glasses, gloves, hearing protection, and chainsaw chaps. Ensure proper chain tension and sharpness. Never operate a damaged saw.

Safety Item	Description
Chain Brake	Quick-stop feature activated by hand guard
Throttle Lockout	Prevents accidental throttle engagement
Right-Hand Guard	Protects from chain breakage
Anti-Vibration System	Reduces operator fatigue
Muffler	Reduces noise and directs exhaust away
Chain Catcher	Stops broken chain from hitting operator
Stop Switch	Immediate engine shut-off
Debris Shield	Protects carburetor from sawdust

Specifications & Features

Engine: Single-cylinder, two-stroke, air-cooled.
Displacement: 31.8 cc.
Power Output: 1.8 kW (2.4 hp).
Fuel Tank Capacity: 0.25 L.
Oil Tank Capacity: 0.20 L.
Chain Pitch: 3/8" PMM.
Bar Length Options: 12" to 16".
Weight (without bar/chain): 4.2 kg.
Ignition: Electronic, non-adjustable.
Carburetor: Zama diaphragm type.

WARNING! Use only STIHL-approved fuel mix (50:1 gasoline to two-stroke oil).

Maintenance Schedule

Regular maintenance ensures optimal performance and safety.

Daily: Check chain tension and sharpness; clean air filter; inspect bar for wear.
Weekly: Clean spark arrestor screen; check fuel lines for cracks.
Monthly: Replace spark plug; clean carburetor; check anti-vibration mounts.
Seasonally: Replace fuel filter; inspect clutch and sprocket; check all safety devices.

CAUTION! Always disconnect spark plug before performing maintenance.

Troubleshooting Guide

Symptom	Possible Cause	Corrective Action
Engine won't start	No spark, flooded carburetor, old fuel	Check spark plug; clean carburetor; use fresh fuel mix.
Engine runs poorly	Clogged air filter, dirty spark arrestor	Clean/replace air filter; clean spark arrestor screen.
Chain won't turn	Clutch worn, sprocket damaged, chain brake engaged	Inspect clutch and sprocket; disengage chain brake.
Excessive vibration	Loose bolts, worn anti-vibration mounts	Tighten all fasteners; replace mounts.
Oil not feeding	Clogged oil passages, faulty oil pump	Clean oil ports; test and replace oil pump if needed.

Engine Repair

Disassembly steps for cylinder, piston, and crankshaft.

Remove top cover and air filter assembly.
Disconnect fuel lines and remove carburetor.
Remove muffler and cylinder cover.
Unbolt cylinder and inspect piston and rings.
Check crankshaft bearings for play.
Reassemble with new gaskets; torque bolts to specification.

Note: Use STIHL tool kit for specialized fasteners.

Fuel System

Carburetor adjustment and fuel line replacement.

Clean external surfaces before disassembly.
Remove diaphragm and check for cracks.
Clean jets with compressed air (never wire).
Set idle screw (L) and high-speed screw (H) to factory settings.
Replace fuel filter and lines if hardened or cracked.

Tip: Always pressure-test fuel system for leaks after repair.

Ignition System

Testing and replacing ignition coil and spark plug.

Remove spark plug; check gap (0.5 mm).
Test for spark by grounding plug against cylinder.
If no spark, check coil resistance (primary: 0.5-1.5 Ω, secondary: 8-15 kΩ).
Replace coil if out of specification.
Ensure stop switch wire is not shorted.

WARNING! Never test spark with plug in contact with fuel mixture.

Chain & Bar Assembly

Proper installation, tensioning, and sharpening.

Place bar on studs; align chain with drive sprocket.
Adjust tension so chain snaps back when pulled from bar.
Tighten bar nuts securely.
Sharpen chain with round file matching cutter size.
File depth gauges to maintain proper clearance.

CAUTION! Always wear gloves when handling chain.

Controls & Safety Devices

Inspection and adjustment of throttle, choke, and chain brake.

Component	Function Test	Adjustment
Throttle Lockout	Must depress before throttle engages	Bend lever if too loose
Chain Brake	Activate by pushing hand guard forward	Replace brake band if worn
Stop Switch	Immediately kills engine	Check wire continuity
Choke Lever	Closes carburetor for cold start	Lubricate linkage

Parts List & Diagrams

Refer to STIHL parts catalog 018-200 for exploded views and part numbers. Common replacement parts:

Piston Kit (1125 030 2003)
Cylinder (1125 020 2001)
Carburetor Repair Kit (1128 007 1000)
Ignition Coil (1128 400 1301)
Clutch Assembly (1125 160 2001)
Oil Pump (1125 650 2001)

Note: Always use genuine STIHL parts for warranty compliance.

Warranty & Support

STIHL 018 chainsaws are covered by a limited warranty for defects in materials and workmanship. Warranty is void if non-approved parts are used or repairs are performed by unauthorized personnel.

Support: Contact STIHL USA at 1-800-467-8445 or visit www.stihlusa.com. For technical assistance, consult an authorized STIHL servicing dealer.

Safety Recall Information: Check website for any active recalls on your model.