MS170 Stihl Chainsaw Manual

The Stihl MS170 is a lightweight, easy-to-use chainsaw designed for homeowners and occasional users. It features a low-emission engine, easy-start system, anti-vibration handles, chain brake, and tool-less chain tensioning. Below are key sections for safety, features, operation, maintenance, and troubleshooting.

Features at a Glance

Key components: Engine, guide bar, saw chain, chain brake, fuel tank, oil tank, throttle trigger, and master control lever.

Feature	Description
Engine	STIHL 2-MIX engine technology for reduced fuel consumption and emissions
Easy2Start™	Simplified starting system requiring less pulling force
Chain Brake	Inertia-activated safety feature to stop chain rotation in kickback situations
Anti-Vibration System	Reduces vibration for increased comfort during operation
Tool-Free Chain Tensioning	Allows for quick chain adjustment without tools
Side Access Chain Tensioner	Conveniently located for easy adjustments
Ematic™ Lubrication System	Efficient chain oil delivery system
QuickStop® Inertia Chain Brake	Additional safety feature that activates during kickback
Fuel Tank Capacity	8.5 fl. oz. (0.25 liter)
Oil Tank Capacity	5.1 fl. oz. (0.15 liter)

Safety Information

Read and understand all safety instructions before operating the chainsaw.

1. Always wear proper PPE: safety glasses, hearing protection, gloves, chainsaw chaps, and sturdy boots.
2. Never operate the chainsaw with one hand.
3. Keep bystanders and pets at least 20 feet away.
4. Be aware of kickback zone - upper quadrant of guide bar tip.
5. Never cut above shoulder height.
6. Always carry chainsaw with engine stopped and guide bar pointed backward.

WARNING! Chainsaws are dangerous tools that can cause serious injury or death. Proper training and safety equipment are essential.

Assembly & Preparation

Assemble your chainsaw following these steps:

1. Attach guide bar: Remove bar cover, place bar on studs, align chain on bar sprocket.
2. Install chain: Ensure cutting teeth face 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. Fill fuel tank: Use STIHL MotoMix® or 50:1 fuel mixture (50 parts gasoline to 1 part STIHL HP Ultra oil).
5. Fill oil tank: Use STIHL chain oil or equivalent.
6. Check chain brake: Ensure it functions properly before starting.

CAUTION! Use only STIHL-approved fuels and lubricants. Never use automotive oil in the fuel mixture.

Specifications

• Engine Displacement: 1.45 cu. in. (30.1 cc)
• Power Output: 1.5 kW (2.0 bhp)
• Weight (without cutting attachment): 6.8 lbs. (3.1 kg)
• Guide Bar Lengths: 12", 14", 16" (available options)
• Chain Pitch: 3/8" PMM3
• Chain Gauge: 0.043" (1.1 mm)
• Fuel/Oil Ratio: 50:1 (STIHL MotoMix® recommended)
• Sound Pressure Level: 103 dB(A)
• Vibration Level: 4.5 m/s² (left/right handles)

Controls and Components

Master Control Lever: Combines choke, throttle lock, and stop functions. Throttle Trigger: Controls engine speed. Throttle Trigger Lockout: Must be depressed before throttle can be engaged. Chain Brake Lever: Manual activation of chain brake. Decompression Valve: Reduces compression for easier starting. Fuel Cap: Twist-off design with integrated tank vent. Oil Cap: For chain oil reservoir.

Starting Sequence: Set master control to choke position (cold start) or half-throttle position (warm start). Press decompression valve (if equipped). Pull starter handle until engine fires.

Starting & Stopping

Cold Start Procedure:

1. Place chainsaw on firm ground.
2. Engage chain brake by pushing lever forward.
3. Set master control lever to choke position (full down).
4. Press decompression valve (if equipped).
5. Pull starter rope sharply until engine fires (usually 2-5 pulls).
6. Move master control to half-throttle position.
7. Pull starter rope again to start engine.
8. Briefly blip throttle to disengage fast idle.

Stopping: Release throttle, allow engine to idle, push master control to stop position.

Tip: Always engage chain brake when starting, carrying, or setting down the chainsaw.

Operating Instructions

Proper cutting techniques for safety and efficiency:

1. Felling trees: Use proper notch and back cut techniques. Always have escape path planned.
2. Limbing: Work from trunk outward. Be aware of spring poles and tensioned branches.
3. Bucking: Support logs properly. Cut from top down for supported logs, bottom up for suspended logs.
4. Pruning: Use light touch. Let chain do the work - don't force the saw.
5. Kickback prevention: Maintain firm grip, don't cut with bar tip, use reduced-kickback chain.
6. Proper stance: Feet shoulder-width apart, left foot slightly forward for right-handed users.

WARNING! Never operate chainsaw when fatigued, under influence of medication/alcohol, or in poor weather conditions.

Maintenance & Cleaning

Regular maintenance ensures optimal performance and safety:

1. Daily: Clean air filter, check chain tension, sharpen chain, clean saw body.
2. Weekly: Clean spark arrestor screen, check spark plug, clean cooling fins.
3. Monthly: Check fuel filter, replace air filter if needed, check all fasteners.
4. Seasonal: Replace spark plug, clean carburetor, check anti-vibration elements.

Cleaning: Use brush and compressed air. Never use water or pressure washer.

CAUTION! Always disconnect spark plug wire before performing maintenance.

Chain & Bar Care

Proper chain maintenance is critical for performance and safety:

1. Sharpening: Use round file matching chain pitch. Maintain correct filing angle (usually 30°).
2. Depth gauges: File rakers to proper height (0.025" below cutting tooth).
3. Bar maintenance: Clean bar groove regularly, flip bar monthly for even wear.
4. Lubrication: Always run with oiler engaged. Check oil flow before each use.
5. Tension: Chain should be snug but pull freely around bar. Re-tension when warm.

Signs of worn chain: Produces fine dust instead of chips, cuts crooked, requires excessive force.

Storage

Proper storage prevents fuel system issues:

1. Long-term storage: Drain fuel tank and run carburetor dry.
2. Short-term storage: Use fuel stabilizer if storing with fuel.
3. Clean entire saw thoroughly before storage.
4. Remove chain, clean and oil it separately.
5. Store in dry place, protected from dust and moisture.
6. Cover bar and chain to prevent rust.

CAUTION! Never store chainsaw with fuel in tank for more than 30 days without stabilizer.

Troubleshooting

Symptom	Possible Cause	Corrective Action
Engine won't start	No spark, flooded, stale fuel	Check spark plug, use fresh fuel, follow starting procedure exactly
Engine starts then dies	Clogged fuel filter, dirty air filter	Replace fuel filter, clean air filter
Poor cutting performance	Dull chain, improper tension	Sharpen chain, adjust tension, check bar groove
Chain won't stay lubricated	Clogged oiler, empty oil tank	Clean oil passages, fill oil tank, check oil pump
Excessive vibration	Loose components, worn AV mounts	Tighten all fasteners, replace anti-vibration elements
Chain won't stop rotating	Chain brake malfunction	Clean brake band, check spring tension, service at dealer
Overheating	Dirty cooling fins, lean fuel mixture	Clean cooling fins, check carburetor adjustment

Service Intervals: First service after 5 hours, then annually or every 50 hours.

Authorized Service: Contact STIHL dealer for repairs. Find dealer at www.stihlusa.com or call 1-800-467-8445.