Stihl MS 260 Service Manual

The Stihl MS 260 is a professional-grade chainsaw featuring a high-performance engine, anti-vibration system, quickstop chain brake, and STIHL Ematic lubrication system. This manual provides essential information for safe operation, routine maintenance, troubleshooting, and repair procedures to ensure optimal performance and longevity of your chainsaw.

Safety Precautions & Warnings

Operating and servicing a chainsaw involves significant risks. Always prioritize personal safety and follow all manufacturer guidelines.

Specifications & Technical Data

• Engine Type: STIHL single-cylinder, two-stroke engine.
• Displacement: 50.2 cm³ (3.06 cu. in.).
• Power Output: 2.6 kW (3.5 bhp).
• Fuel/Oil Mix Ratio: 50:1 (STIHL HP Ultra or equivalent).
• Guide Bar Lengths: 16" (40 cm) to 20" (50 cm) recommended.
• Chain Pitch/Gauge: .325" / .063" (1.6 mm).
• Ignition System: Electronic, capacitor discharge (CDI).
• Weight (powerhead): Approximately 5.2 kg (11.5 lbs).
• Sound Pressure Level: ~106 dB(A).
• Vibration Levels: Front/Rear handle: ~4.5/2.5 m/s².

Component Identification

Key components of the Stihl MS 260 chainsaw.

1. Front Handle: Includes throttle trigger, throttle trigger lockout, and hand guard with chain brake.
2. Rear Handle: Contains master control lever (stop switch, choke, fast idle).
3. Fuel Tank: Located at rear of saw. Capacity: 0.5 L (16.9 fl. oz).
4. Oil Tank: For chain lubrication. Capacity: 0.26 L (8.8 fl. oz).
5. Muffler: Equipped with spark arrestor screen.
6. Chain Tensioner: Side-mounted, accessible with combination wrench.
7. Decompression Valve: Reduces pulling force for starting.
8. Air Filter Cover: Secures air filter and fuel lines.

WARNING! Familiarize yourself with all controls before starting the engine.

Daily & Routine Maintenance

Regular maintenance is critical for safety and performance.

1. Before Each Use: Check chain tension, sharpness, and lubrication. Inspect for loose nuts/bolts. Test chain brake function.
2. Air Filter: Clean daily in dusty conditions. Remove, tap clean, or wash in soapy water (if foam). Allow to dry completely before reinstalling.
3. Spark Plug: Check and clean electrode gap (0.5 mm / 0.020") every 10 operating hours. Replace if worn or fouled (STIHL part #0000-400-1301).
4. Chain Sprocket: Inspect for wear (especially rim sprocket). Replace if teeth are hooked or worn.
5. Exterior Cleaning: Keep saw clean of sawdust, oil, and resin. Use a brush and plastic scraper. Avoid water spray.

CAUTION! Always disconnect the spark plug boot before performing any maintenance.

Fuel & Lubrication System

The MS 260 uses a diaphragm carburetor and separate systems for fuel and chain oil.

Tip: Use only STIHL chain oil or equivalent for proper bar and chain lubrication.

Ignition System

Electronic ignition module (CDI) requires no maintenance. Primary service involves the spark plug and stop switch.

1. Spark Plug Check: Remove plug. Electrode gap should be 0.5 mm (0.020"). Clean with wire brush. Replace if insulator is cracked or electrodes are heavily eroded.
2. Ignition Wire: Inspect boot for secure connection to plug. Wire should be intact with no cracks.
3. Stop Switch Test: With spark plug removed and boot secured to ground, pull starter. Engine should not spark when switch is in STOP (0) position.
4. Module Replacement: If no spark, check all connections first. Module is non-repairable; replace if faulty.

Carburetor Adjustment

The carburetor has three adjustment screws: L (low speed), H (high speed), and LA (idle speed).

1. Preliminary: Ensure air filter is clean and spark arrestor screen is clear. Run saw to operating temperature.
2. Idle Speed (LA): Adjust so chain does not move at idle. If chain moves, turn LA screw counter-clockwise slightly.
3. Low Speed (L): Turn L screw clockwise until engine runs smoothly at idle and accelerates cleanly from idle.
4. High Speed (H): WARNING: This screw is limited by a limiter cap. Do not remove cap. Factory setting is usually optimal. Incorrect adjustment can cause engine damage. Consult a STIHL dealer for H adjustment.
5. Final Check: Chain must not move at idle. Engine should return promptly to idle after triggering throttle.

WARNING! Excessive H screw adjustment can cause engine overspeed (racing) leading to severe engine damage.

Chain & Bar Maintenance

Proper care of the cutting attachment is essential for safety and cutting performance.

• Chain Sharpening: Use correct round file size (4.0 mm / 5/32") and file guide. Maintain correct filing angle (30°). File all cutters to equal length. Check depth gauges (rakers) with gauge tool and file down if necessary.
• Chain Tension: Correct tension: snug against bar but pullable by hand. Re-tighten when chain sags (frequent when new). Lift bar tip to check tension.
• Bar Care: Regularly clean bar groove and oil holes. Flip bar weekly for even wear. Dress bar rails with a flat file if burred.
• Sprocket Nose Bar: Grease sprocket nose daily through grease fitting (if equipped).

Disassembly & Assembly Procedures

Major procedures require specific tools and technical knowledge.

1. Removing Engine Covers: Remove nuts/wing nuts from anti-vibration buffers. Carefully separate halves, noting routing of wires and control linkages.
2. Cylinder & Piston Inspection: Remove muffler to inspect piston through exhaust port. Look for scoring or seizure marks. Full disassembly requires removing cylinder base nuts.
3. Clutch & Sprocket: Hold piston at TDC using piston stop tool. Remove clutch nut (left-hand thread) to access clutch drum and sprocket.
4. Reassembly: Use new gaskets. Torque cylinder nuts to specification (typically 10-12 Nm). Ensure all linkages are correctly connected before closing covers.

CAUTION! These are complex procedures. If unsure, seek service from an authorized STIHL dealer.

Troubleshooting Guide

Parts List & Diagrams

For complete parts lists and exploded-view diagrams, refer to the official STIHL MS 260 Parts Catalog. Key assembly groups include:

1. Cylinder, Piston, Crankshaft Assembly
2. Carburetor, Air Filter, Fuel System
3. Ignition Module, Flywheel, Rewind Starter
4. Clutch, Sprocket, Chain Brake Assembly
5. Handles, Anti-Vibration System, Covers
6. Guide Bars and Saw Chains

Service: For genuine STIHL parts, technical bulletins, and dealer support, visit www.stihlusa.com or contact your local authorized STIHL servicing dealer.