Stihl MS261C Manual

The Stihl MS261C is a professional-grade chainsaw featuring a 50.2cc engine with M-Tronic electronic engine management for automatic carburetor adjustment, reduced-emission engine technology, anti-vibration system, STIHL Quickstop® inertia chain brake, side-access chain tensioner, tool-less fuel and oil caps, 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 management system, anti-vibration handles, Quickstop® inertia chain brake, side-access chain tensioner, Ematic™ lubrication system, and decompression valve.

Feature	Description
M-Tronic Engine Management	Automatically adjusts carburetor for optimal performance in varying conditions
Quickstop® Inertia Chain Brake	Stops chain instantly in kickback situations
Anti-Vibration System	Reduces operator fatigue during extended use
Side-Access Chain Tensioner	Allows easy chain adjustment without removing cover
Ematic™ Lubrication System	Reduces bar oil consumption while ensuring proper lubrication
Decompression Valve	Reduces compression for easier starting
Tool-less Fuel & Oil Caps	Easy refueling without tools
STIHL ElastoStart™	Reduces starting effort by up to 40%
Pre-Separation Air Filtration	Extends air filter service intervals
Chain Catchment Sprocket	Helps retain chain if it breaks

Safety Information

Always wear proper protective equipment: helmet with face shield, hearing protection, gloves, chainsaw chaps, and steel-toed boots.

1. Read manual completely before operation.
2. Inspect chainsaw before each use for damage or loose parts.
3. Maintain secure footing and clear work area of obstacles.
4. Never operate with damaged or improperly tensioned chain.
5. Keep bystanders at least 15 feet away during operation.

WARNING! Kickback can occur without warning. Always hold saw firmly with both hands, thumbs wrapped around handles. Never cut above shoulder height.

Assembly & Preparation

Unpack and inspect contents. Assembly requires guide bar and chain installation.

1. Install guide bar: Remove side cover, position bar over studs with tensioning pin in adjustment hole.
2. Install chain: Place chain over bar sprocket with cutting teeth facing forward on top of bar.
3. Adjust chain tension: Use side tensioner to achieve proper tension (chain should snap back when pulled from bar).
4. Fuel mixture: Use STIHL MotoMix® pre-mixed fuel or mix 50:1 with STIHL HP Ultra oil and 89+ octane gasoline.
5. Chain oil: Fill with STIHL chain oil or equivalent.

CAUTION! Use only STIHL-approved replacement parts. Improper assembly can cause serious injury.

Specifications

• Engine Displacement: 50.2 cc
• Power Output: 3.0 bhp (2.2 kW)
• Weight (Powerhead): 10.8 lbs (4.9 kg)
• Fuel Capacity: 16.9 fl oz (500 ml)
• Oil Capacity: 8.5 fl oz (250 ml)
• Guide Bar Lengths: 16" to 20" (recommended 18")
• Chain Pitch: 3/8" PM3
• Chain Gauge: 0.050" (1.3 mm)
• Sound Pressure Level: 106 dB(A)
• Vibration Levels: 4.2 m/s² (front), 2.8 m/s² (rear)

Controls and Components

Main controls: Master Control Lever (combines choke, throttle lock, stop switch), throttle trigger, throttle trigger lockout, chain brake lever, decompression valve, and primer bulb.

Right Side: Chain brake lever, throttle trigger, throttle trigger lockout, rear handle with vibration damping. Left Side: Master Control Lever, decompression valve, primer bulb, fuel and oil caps. Front: Muffler with spark arrestor, chain catcher, bumper spike.

Safety Features: Chain brake (manual and inertia activated), throttle trigger lockout, right-hand guard, chain catchment sprocket.

Starting & Stopping

Cold Start Procedure:

1. Place saw on firm ground, engage chain brake.
2. Press decompression valve (if equipped).
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 (usually 2-3 pulls).
6. Immediately move Master Control Lever to half-throttle position.
7. Pull starter rope again until engine starts.
8. Blip throttle to disengage fast idle.

Warm Start: Master Control Lever in run position (middle), no choke needed.

Stopping: Release throttle, move Master Control Lever to stop position (up).

Operation & Cutting Techniques

Basic cutting positions: felling, limbing, bucking, and pruning.

1. Felling: Plan escape path (45° angle from fall direction). Make notch cut (1/3 tree diameter), then back cut leaving hinge wood.
2. Limbing: Work from trunk outward, keep saw between you and branch being cut.
3. Bucking: Support log properly, cut from top side, avoid pinching chain.
4. Pruning: Use bottom of guide bar, cut in smooth controlled motions.

Tip: Let chain do the work; don't force the saw. Maintain proper chain speed for efficient cutting.

Maintenance Schedule

Interval	Task
Daily/Before Use	Check chain tension, sharpness, and lubrication; inspect for damage
Every 5 Hours	Clean air filter, check spark plug, clean cooling fins
Every 20 Hours	Replace spark plug, clean fuel filter, check anti-vibration elements
Every 50 Hours	Clean exhaust system, check carburetor adjustment (M-Tronic self-adjusts)
Every 100 Hours	Replace fuel filter, check clutch and sprocket
Annually	Professional inspection recommended

WARNING! Always disconnect spark plug before performing maintenance.

Chain Sharpening & Tensioning

Proper chain maintenance ensures safety and performance.

1. Sharpening: Use round file matching chain pitch (5/32" for 3/8" PM3). File each cutter at 30° angle, maintain consistent depth gauge height.
2. Tensioning: Chain should be snug against bar but pull freely. Adjust when chain is warm. Proper tension: chain should snap back when pulled from bar groove.
3. Depth Gauges: File to 0.025" below cutting edge using depth gauge tool.
4. Bar Maintenance: Flip bar regularly, clean bar groove, file burrs from rails.

CAUTION! Wear gloves when handling chain. Dull chain increases kickback risk.

Storage Guidelines

Proper storage prevents fuel system issues and corrosion.

1. Drain fuel tank and run carburetor dry for storage over 30 days.
2. Remove chain, clean and oil it, store separately.
3. Clean entire saw, especially air intake and cooling fins.
4. Store in dry, cool place away from ignition sources.
5. For long-term storage, fog cylinder with preservative oil.

Tip: Use fuel stabilizer if draining isn't possible. Never store with fuel in tank for extended periods.

Troubleshooting

Symptom	Possible Cause	Corrective Action
Engine won't start	Old fuel, flooded engine, spark plug	Use fresh fuel, wait if flooded, check/replace spark plug
Engine starts then dies	Fuel filter clogged, vent blocked	Replace fuel filter, clean tank vent
Poor cutting performance	Dull chain, improper tension	Sharpen chain, adjust tension
Chain won't stop when brake engaged	Brake mechanism dirty/worn	Clean brake band and drum, replace if worn
Excessive vibration	Loose components, damaged AV mounts	Tighten all fasteners, check anti-vibration elements
Chain throws oil	Overfilled oil tank, wrong oil viscosity	Check oil level, use proper chain oil
M-Tronic not adjusting properly	System needs reset	Run at full throttle for 1 minute; if issues persist, see dealer

Reset M-Tronic: Start engine, run at full throttle for 1 minute without cutting to allow system to recalibrate.

Service: Authorized STIHL dealers only. Visit www.stihlusa.com or call 1-800-467-8445 for dealer locator.