STIHL MS 260 Service Repair Manual

The STIHL MS 260 is a professional-grade chainsaw featuring a high-performance engine, anti-vibration system, and STIHL Quickstop® inertia chain brake. This service and repair manual provides detailed instructions for maintenance, troubleshooting, disassembly, and reassembly. Below are key sections covering safety, specifications, maintenance procedures, fuel system, ignition system, cooling system, clutch/chain brake, and troubleshooting.

Features at a Glance

Key components: Engine cylinder, carburetor, ignition module, anti-vibration system, chain brake, oil pump, air filter, spark plug, and muffler.

Safety Precautions

Always wear protective equipment. Disconnect spark plug before service.

1. Personal Protective Equipment: Wear safety glasses, gloves, hearing protection, and chainsaw chaps.
2. Work Area: Ensure clean, well-lit, and ventilated space free of flammable materials.
3. Fuel Safety: Drain fuel before service. Use approved containers.
4. Chain Safety: Ensure chain brake is engaged and chain is properly tensioned.

WARNING! Failure to follow safety procedures may result in serious injury or death. Always refer to the operator's manual for safe operation.

Specifications

• Engine Type: Single cylinder, two-stroke, air-cooled.
• Bore x Stroke: 44 mm x 33 mm.
• 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").
• Fuel Mix: 50:1 (STIHL HP Ultra oil with unleaded gasoline).
• Carburetor Settings (initial): LA: 1 turn open, H: 1 turn open, L: 1 turn open.
• Chain Oil: STIHL chain oil or equivalent.
• Warranty: Refer to STIHL warranty terms.

Maintenance Schedule

Regular maintenance ensures optimal performance and longevity.

Daily: Clean air filter, check chain tension and sharpness, inspect for loose fasteners.

Weekly: Clean cooling fins, check spark plug condition, inspect fuel filter.

Monthly: Clean carburetor air passage, check anti-vibration elements, inspect clutch drum and sprocket.

Annually: Replace fuel filter, inspect ignition module, check cylinder compression.

Fuel System Service

Fuel system includes tank, filter, lines, and carburetor.

1. Drain fuel tank completely.
2. Replace fuel filter using filter pick or hook.
3. Inspect fuel lines for cracks or leaks; replace if necessary.
4. Clean fuel tank vent.
5. Check carburetor diaphragm and gaskets for wear.

Tip: Use STIHL fuel line replacement kit for proper fit.

Ignition System Service

Ignition system includes spark plug, wire, and module.

1. Remove spark plug and check electrode gap; adjust to 0.5 mm.
2. Test spark by grounding plug against cylinder; pull starter to check for spark.
3. Inspect ignition wire for cracks or damage.
4. Check flywheel key for shear; replace if damaged.
5. Test ignition module resistance per STIHL specifications.

WARNING! Never test for spark with plug removed and wire near open fuel source.

Cooling System Service

Cooling system includes cylinder fins, fan wheel, and air intake.

1. Remove debris from cylinder cooling fins using brush or compressed air.
2. Inspect fan wheel on flywheel for damage or cracks.
3. Clean air intake slots on starter housing.
4. Check spark arrestor screen in muffler; clean or replace if clogged.

CAUTION! Overheating can cause engine seizure. Ensure cooling system is clean.

Clutch & Chain Brake Service

Clutch engages chain; chain brake stops chain in event of kickback.

1. Remove clutch cover, chain, and bar.
2. Inspect clutch drum for wear; replace if grooved.
3. Check clutch springs for fatigue; replace if stretched or broken.
4. Test chain brake function by manually triggering brake band.
5. Inspect brake band and linkage for wear or damage.

WARNING! Always test chain brake after service to ensure proper operation.

Carburetor Adjustment

Adjust carburetor for optimal performance at operating temperature.

1. Start engine and warm up for several minutes.
2. Set idle speed screw (LA) to achieve 2,800 rpm.
3. Adjust low speed screw (L) for smooth acceleration.
4. Adjust high speed screw (H) for maximum power without over-revving.
5. Re-check idle speed after adjustments.

Note: Use tachometer for precise adjustment. Final settings may vary based on altitude and temperature.

Disassembly & Reassembly

Major disassembly requires proper tools and attention to detail.

1. Remove top cover, starter assembly, and air filter housing.
2. Remove cylinder cover and muffler.
3. Disconnect fuel lines and remove carburetor.
4. Remove cylinder bolts and carefully lift cylinder.
5. Inspect piston and cylinder for scoring; measure ring end gap.
6. Reassemble in reverse order using new gaskets.

CAUTION! Torque all fasteners to STIHL specifications. Use genuine STIHL parts.

Troubleshooting

Reset: For electronic ignition issues, ensure flywheel key is intact.

Service: For technical support, contact STIHL authorized service center or visit www.stihlusa.com.