STIHL MS 291 Chainsaw Manual

The STIHL MS 291 is a professional-grade, mid-range chainsaw featuring a powerful 55.5 cc engine with STIHL M-Tronic engine management for automatic adjustment to fuel quality and environmental conditions. It includes an anti-vibration system, QuickStop® inertia chain brake, Ematic™ lubrication system, side-access chain tensioner, and toolless fuel and oil caps. Below are key sections for safety, features, assembly, operation, maintenance, and troubleshooting.

Features at a Glance

Key components: Engine with M-Tronic, anti-vibration system, QuickStop® chain brake, side-access chain tensioner, Ematic™ lubrication, toolless caps.

Safety Information

Read manual before use. Wear proper PPE: helmet, eye/ear protection, gloves, chainsaw chaps, and boots.

1. Clear work area of obstacles and people.
2. Check chain tension, sharpness, and lubrication before each use.
3. Hold saw firmly with both hands; right hand on rear handle, left on front.
4. Be aware of kickback zone (upper quadrant of bar tip).
5. Never operate above shoulder height or on a ladder.

WARNING! Chainsaw kickback can cause severe injury or death. Always use chain brake and proper technique.

Assembly & First Use

Unpack and inspect contents. Assemble guide bar and chain.

1. Attach guide bar: Place bar on studs, align chain with sprocket, fit chain around bar.
2. Tension chain: Use side tensioner to adjust until chain snaps back when pulled from bar.
3. Fill fuel: Use STIHL MotoMix® or 50:1 mix of 89+ octane gas and STIHL HP Ultra oil.
4. Fill chain oil: Use STIHL chain oil or equivalent.
5. Prime fuel system: Press primer bulb 5-10 times until fuel is visible.

CAUTION! Fuel is highly flammable. Refuel in well-ventilated area, away from ignition sources.

Specifications

• Displacement: 55.5 cc.
• Power Output: 3.4 bhp (2.5 kW).
• Fuel Capacity: 16.9 fl oz (500 ml).
• Oil Capacity: 11.8 fl oz (350 ml).
• Sound Pressure Level: 106 dB(A).
• Vibration Levels (front/rear): 4.5/2.5 m/s².
• Chain Pitch/Gauge: 3/8" PM / .050" (1.3 mm).
• Ignition: Electronic, capacitor discharge.
• Warranty: Limited 1-year commercial, 2-year residential.

Controls and Components

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

Components: Front handle with hand guard, rear handle, spark plug cover, air filter cover, muffler, guide bar, chain catcher, toolless caps.

Operation: Master Control lever positions: STOP (0), RUN (I), START/CHOKE (⏻). Chain brake: Push forward to engage (lock), pull back toward handle to disengage.

Starting & Stopping

Cold Start: Engage chain brake. Set Master Control to START/CHOKE. Press decompression valve. Pull starter rope until engine fires. Move lever to RUN. Pull again to start. Warm Start: Set lever to RUN and pull.

1. Place saw on firm ground, hold rear handle with right foot.
2. Pull starter handle slowly until resistance felt, then briskly.
3. After starting, blip throttle to disengage fast idle.
4. To stop: Move Master Control lever to STOP (0).

Tip: Always engage chain brake when starting or carrying saw.

Operation & Cutting Techniques

Supports felling, limbing, bucking, and pruning.

1. Felling: Plan escape path. Make notch cut (1/3 diameter), then felling cut (leave hinge).
2. Limbing: Stand uphill, cut from trunk outward, support limb if needed.
3. Bucking: Support log; use undercut for top bind, overcut for bottom bind.
4. Pruning: Use pulling chain (bottom of bar) for control.
5. Kickback Prevention: Keep tip guard on; avoid contact with tip; hold firmly.
6. Chain Speed: Maintain full throttle during cuts; do not "ride" the chain brake.

WARNING! Do not cut with the upper quadrant of bar tip. Watch for falling limbs.

Maintenance Schedule

Daily: Check chain tension, sharpness, lubrication. Clean air filter, check for loose parts. Weekly: Clean cooling fins, spark arrestor screen. Monthly: Replace spark plug, fuel filter, clean carburetor air passage. As needed: Replace chain, bar, sprocket.

Chain Care & Sharpening

Keep chain sharp for efficiency and safety. Use round file and guide matching chain pitch.

1. Secure bar. File each cutter from inside out at 30° angle.
2. Maintain depth gauges (rakers) with flat file; height 0.025" (0.65 mm) below cutter.
3. Check for even cutter length; shorten longer cutters to match.
4. Lubricate chain with oil after sharpening.

CAUTION! Wear gloves. File in one direction only; do not drag back.

Storage

Long-term: Drain fuel tank and run engine dry. Remove chain, clean and oil it. Store in dry place. Short-term: Store with full fuel tank (with stabilizer if over 30 days).

CAUTION! Fuel left in carburetor can cause starting issues. Use fuel stabilizer.

Troubleshooting

Reset M-Tronic: Start and run at full throttle for 1 minute (if equipped).

Service: Authorized STIHL dealer only. Find at www.stihlusa.com.