STIHL 025 Chainsaw Repair Manual

The STIHL 025 is a professional-grade chainsaw designed for demanding cutting tasks. This repair manual provides comprehensive instructions for troubleshooting, maintenance, and repair of the STIHL 025 chainsaw, including engine, fuel system, ignition, chain brake, bar, and chain components. Below are key sections covering safety, specifications, disassembly, troubleshooting, and reassembly procedures.

1. Safety Precautions 2. Specifications 3. Tools Required 4. Engine Disassembly 5. Fuel System Repair 6. Ignition System 7. Chain Brake System 8. Bar and Chain Maintenance 9. Reassembly Instructions 10. Troubleshooting Guide 11. Parts Diagram & Ordering

Safety Precautions

Always prioritize safety when performing repairs. Key safety components: Chain brake, throttle lockout, front and rear hand guards.

Safety Feature	Description
Chain Brake	Stops chain rotation in kickback situations
Throttle Lockout	Prevents accidental throttle engagement
Front Hand Guard	Protects hand from chain contact
Rear Hand Guard	Provides additional hand protection
Muffler	Reduces exhaust noise and directs heat away
Chain Catcher	Catches broken chain to prevent injury
Right Hand Guard	Protects right hand during operation
Stop Switch	Immediately stops engine when engaged
Master Control Lever	Combines choke, throttle, and stop functions
Anti-Vibration System	Reduces vibration to operator

Specifications

Unpack and inspect contents. Place on stable work surface.

Engine Type: Single cylinder, two-stroke, air-cooled.
Displacement: 45.4 cc (2.77 cu. in.).
Power Output: 2.2 kW (3.0 hp).
Fuel Tank Capacity: 0.55 L (18.6 fl. oz.).
Oil Tank Capacity: 0.26 L (8.8 fl. oz.).
Bar Length Options: 40 cm (16"), 45 cm (18").
Chain Pitch: 3/8" PMM.
Weight (without bar & chain): 5.2 kg (11.5 lbs).
Ignition System: Electronic, breakerless.
Spark Plug: Bosch WSR 6F or equivalent.

WARNING! Always wear protective gloves and eyewear. Ensure chainsaw is cool before starting repairs.

First-Time Setup

Gather all necessary tools before beginning repair.

Remove spark plug wire: Disconnect to prevent accidental starting.
Drain fuel and oil: Tilt saw to drain into approved containers.
Clean exterior: Remove dirt and debris from housing.
Secure chainsaw: Use vise or clamp to hold saw securely.

CAUTION! Work in well-ventilated area. Keep away from open flames.

Specifications

Engine: 45.4 cc two-stroke, air-cooled.
Fuel Mix: 50:1 (Gasoline:STIHL HP Ultra Oil).
Chain Oil: STIHL Chain Oil or equivalent.
Idle Speed: 2,800 RPM.
Maximum Power Speed: 9,500 RPM.
Sound Pressure Level: 106 dB(A).
Vibration Level: 4.5 m/s² front handle, 6.5 m/s² rear handle.
Warranty: 1 year commercial use, 2 year private use.

Controls and Settings

Access components by removing housing screws. Front Housing: Master control lever, throttle trigger, throttle lockout.

Engine Components: Cylinder, piston, carburetor, ignition module, flywheel, starter assembly.

Fuel System: Fuel tank, fuel filter, fuel lines, carburetor (adjustment screws: L, H, LA). Ignition: Spark plug, ignition module, stop switch, wiring. Chain Drive: Sprocket, clutch, chain tensioner. Chain Brake: Band, spring, activation lever.

Connecting Devices

Special tools required: STIHL piston stop, flywheel puller, clutch tool, compression tester.

Turn off fuel valve and disconnect spark plug.
Match tools to specific fasteners (Torx, hex, spline).
Organize parts in order of removal for reassembly.

Tip: Take photos during disassembly to aid reassembly.

Playing DVD Media

Supports standard repair procedures and special service techniques.

Remove housing: Take out all housing screws, note locations.
Disconnect linkages: Throttle cable, choke rod, stop switch wires.
Remove engine components: Cylinder head, piston, carburetor.
Inspect: Check piston for scoring, cylinder for wear.
Clean: Remove carbon deposits from exhaust port and piston.
Measure: Check piston ring gap, cylinder bore.
Replace: Install new gaskets, seals, worn parts.
Reassemble: Reverse disassembly order with new fasteners.

WARNING! Do not force components. Use proper tools to avoid damage.

Accessibility Features

Carburetor Adjustment: Adjust L (low speed), H (high speed), LA (idle) screws. Chain Tension: Adjust via side tensioner screw. Chain Brake Test: Engage brake, pull throttle to verify function.

Care & Cleaning

Clean air filter regularly. Use compressed air to clean cooling fins. Sharpen chain regularly with proper filing tools.

CAUTION! Never use gasoline for cleaning. Use approved degreasers only.

Regulatory Information

EPA Certified: Meets EPA emission standards. CARB Compliant: Approved for California use. EU Emission Standards: Meets Stage II requirements. Copyright © STIHL Incorporated; all rights reserved. For technical support, visit www.stihlusa.com or contact 1-800-467-8445.

Troubleshooting

Symptom	Possible Cause	Corrective Action
Engine won't start	Fuel, spark, compression	Check fuel mix, spark plug, compression (should be 120+ psi).
Engine runs poorly	Carburetor, air filter	Clean/replace air filter; adjust carburetor; check fuel lines.
Chain won't turn	Clutch, sprocket, brake	Disengage chain brake; inspect clutch springs; replace worn sprocket.
Excessive vibration	Mounts, balance	Check anti-vibration mounts; ensure bar and chain are properly balanced.
Oil not feeding	Oil pump, passages	Clean oil passages; check oil pump drive; adjust oil flow screw.

Reset: After repair, reset carburetor to factory settings: L-1 turn, H-1 turn from lightly seated.

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