Stihl 261 Manual

The Stihl MS 261 is a professional-grade chainsaw featuring a 50.2 cc engine, STIHL M-Tronic engine management for automatic adjustment to fuel quality and environmental conditions, an anti-vibration system, Ematic lubrication system for reduced oil consumption, QuickStop Super inertia chain brake, side-access chain tensioner, and a decompression valve for easier starting. Below are key sections for safety, features, operation, maintenance, and troubleshooting.

Features at a Glance

Key components: M-Tronic engine, anti-vibration system, QuickStop Super chain brake, side-access chain tensioner, Ematic lubrication, and decompression valve.

Feature	Description
Engine Displacement	50.2 cc
Engine Management	STIHL M-Tronic (auto-adjusts carburetion)
Guide Bar Lengths	Typically 16" to 20"
Chain Pitch/Gauge	.325" / .063" (common)
Anti-Vibration System	Reduces operator fatigue
Chain Brake	QuickStop Super inertia-activated
Lubrication System	Ematic (efficient oil delivery)
Decompression Valve	Eases starting effort
Fuel Tank Capacity	Approx. 0.53 US pt (0.25 l)
Oil Tank Capacity	Approx. 0.42 US pt (0.20 l)

Safety Information

Read and understand all safety warnings before operation.

1. Personal Protective Equipment (PPE): Always wear chainsaw chaps, safety glasses, hearing protection, gloves, and steel-toe boots.
2. Work Area Safety: Keep bystanders and pets at least 15 feet away. Ensure secure footing.
3. Kickback Zone: Be aware of the upper quadrant of the guide bar tip. Do not cut with this area.
4. Chain Brake: Test function before each use. Carry saw with brake engaged.

WARNING! Failure to follow safety instructions can result in serious injury or death. The chain brake is not a substitute for safe operating practices.

Assembly & Preparation

Assemble the saw from the box for first-time use.

1. Attach Guide Bar & Chain: Place bar on studs, loop chain onto bar (cutting edges facing forward on top), tension appropriately, and secure side cover.
2. Fill Fluids: Use STIHL MotoMix® or 50:1 fuel/oil mixture (89 octane min.). Fill chain oil reservoir with STIHL chain oil.
3. Check Chain Tension: Chain should be snug against bar but pull freely by hand. Re-tension when cold.
4. Lubrication Check: Run saw at high idle over light-colored surface to confirm oil is reaching the chain.

CAUTION! Use only STIHL-approved fuels, oils, and lubricants. Improper mixtures can cause engine damage.

Specifications

• Model: STIHL MS 261
• Engine Type: 2-stroke, single cylinder
• Displacement: 50.2 cc (3.06 cu. in.)
• Power Output: 3.0 bhp (2.2 kW)
• Weight (powerhead): 10.8 lbs (4.9 kg)
• Fuel/Oil Ratio: 50:1 (STIHL 2-stroke oil)
• Ignition System: Electronic, M-Tronic
• Chain Brake: QuickStop Super (inertia)
• Sound Pressure Level: Approx. 106 dB(A)
• Vibration Levels (front/rear): Approx. 4.2/2.5 m/s²

Controls and Components

Familiarize yourself with all controls before starting.

Main Controls: Master Control Lever (combines choke, throttle lock, stop control), Throttle Trigger, Throttle Trigger Lockout, Chain Brake Lever (front hand guard), Decompression Valve Button, and Primer Bulb.

Features: M-Tronic does not have manual adjustment screws. Side-access chain tensioner allows adjustment without removing side cover. Ematic oiler has standard and high-output settings (via screw).

Starting & Stopping

Cold Start (with Decompression Valve):

1. Engage chain brake. Place saw on firm ground.
2. Press decompression valve.
3. Set Master Control lever to choke position (full down).
4. Press primer bulb 5-6 times until fuel is visible.
5. Pull starter rope sharply until engine 'fires' once.
6. Move Master Control lever to half-throttle position (mid-notch).
7. Pull starter rope again to start. Let run for a moment.
8. Squeeze throttle trigger to disengage fast-idle.

Warm Start: Master Control lever to half-throttle position only. Do not use choke or primer.

Stopping: Release throttle, allow to idle briefly, then push Master Control lever up to STOP position.

Operation & Cutting Techniques

Use proper techniques to maintain control and reduce kickback risk.

1. Basic Stance: Feet shoulder-width apart, left foot slightly forward. Hold saw firmly with both hands.
2. Felling: Use proper notch and backcut techniques. Plan escape path. Use wedges.
3. Limbing: Stand on opposite side of tree from limbs being cut. Let the chain do the work.
4. Bucking: Support logs properly. Cut from top to avoid pinching. Use a plastic or wooden wedge if needed.
5. M-Tronic Calibration: After initial start or major altitude/temp change, run saw at full throttle for 1 minute (no load) to allow system to adapt.

Tip: Keep the chain sharp. A dull chain increases effort, wear, and kickback danger.

Maintenance Schedule

Interval	Task
Daily / Before Use	Check chain tension, sharpness, and lubrication. Inspect for loose fasteners. Clean air intake and saw body.
Every 5 Hours	Clean spark plug, check electrode gap (0.020"). Clean air filter (more often in dusty conditions).
Every 20 Hours	Replace spark plug. Check fuel filter and replace if clogged.
Every 100 Hours	Clean cylinder fins. Check anti-vibration elements. Have dealer check M-Tronic system.
Annually / 50 Hours	Replace fuel line and filter. Clean exhaust screen/spark arrestor (if equipped).

Chain & Bar Care

Proper care extends life and ensures safety.

1. Sharpening: Use correct round file size (.325" chain uses a 3/16" file). Maintain correct filing angle (typically 30°). File all cutters to equal length.
2. Depth Gauges: File down depth gauges (rakers) with a flat file and gauge tool to maintain proper height difference (approx. 0.025").
3. Bar Maintenance: Flip bar regularly for even wear. Clean bar groove and oil holes. Dress bar rails with a flat file if burred.
4. Tensioning: Always tension chain when cold. Correct tension: snug against bar bottom, but pull freely by hand.

CAUTION! Always wear heavy gloves when handling the chain.

Storage

Prepare saw for storage periods longer than 30 days.

1. Drain fuel tank completely and run engine until it stops to clear carburetor.
2. Remove chain, clean it, and store in oil. Clean guide bar and coat with oil.
3. Clean entire saw, especially cooling fins and air filter.
4. Store in a dry, secure place, away from children.

WARNING! Never store saw with fuel in the tank for extended periods. Fuel can degrade and damage engine components.

Troubleshooting

Symptom	Possible Cause	Corrective Action
Engine will not start	No spark, flooded, stale fuel, Master Control position	Check spark plug. Use correct starting procedure. Use fresh fuel mix. Ensure brake is engaged for starting.
Engine starts then dies	Clogged air filter, fuel filter, or tank vent. M-Tronic adapting.	Clean/replace filters. Run at full throttle for 1 min (no load) to allow adaptation.
Loss of power	Dull chain, clogged spark arrestor, dirty air filter, improper fuel	Sharpen chain. Clean spark arrestor screen. Clean air filter. Use fresh 50:1 mix.
Chain does not oil	Empty oil tank, clogged oil holes, wrong oiler setting	Fill tank. Clean bar oil holes and saw outlet. Check oiler screw setting.
Excessive vibration	Loose components, damaged anti-vibration mounts, unbalanced chain	Tighten all fasteners. Inspect AV mounts. Check chain for damaged/different cutter lengths.

Reset M-Tronic: If experiencing persistent running issues, a dealer can perform a software reset on the M-Tronic module.

Service: For repairs beyond basic maintenance, contact an authorized STIHL servicing dealer.