MS170 Stihl Chainsaw Manual

The Stihl MS170 is a lightweight, easy-to-use chainsaw designed for homeowners and occasional users. It features a powerful gasoline engine, low-emission technology, an anti-vibration system, a side-access chain tensioner, and STIHL's Quickstop® inertia chain brake for enhanced safety. Below are key sections for safety, features, assembly, operation, maintenance, and troubleshooting.

Features at a Glance

Key components: Gasoline engine with electronic ignition, guide bar, saw chain, chain brake, throttle trigger lockout, and anti-vibration system.

Assembly & Preparation

Unpack and inspect all parts. Assemble on a clean, stable surface.

1. Attach Guide Bar and Chain: Place bar on studs, loop chain over sprocket and bar, adjust tension with side wheel.
2. Fill Fuel: Use STIHL MotoMix® pre-mixed fuel or mix high-quality 2-stroke oil (50:1 ratio) with unleaded gasoline (min. 89 octane).
3. Fill Chain Oil: Use STIHL chain oil or a quality biodegradable bar & chain oil.
4. Check Controls: Ensure throttle trigger, trigger lockout, and chain brake function smoothly.

WARNING! Always wear appropriate Personal Protective Equipment (PPE): safety glasses, hearing protection, gloves, chainsaw chaps, and sturdy boots.

First-Time Operation

Before first start, perform a safety check.

1. Check Chain Tension: Chain should be snug against bar but pull freely by hand.
2. Check Chain Sharpness: Ensure cutters are sharp and depth gauges are properly filed.
3. Clear Work Area: Remove tripping hazards and ensure bystanders are at least 15 feet away.
4. Start Saw: Place on firm ground, engage chain brake, set master control lever to cold start position, pull starter rope until engine fires.

CAUTION! Never start the saw in a closed area. Ensure the chain does not contact any object when starting.

Specifications

• Engine Type: Single cylinder, 2-stroke, air-cooled.
• Power Output: 1.5 kW (2.0 bhp).
• Fuel/Oil Ratio: 50:1 (STIHL 2-stroke oil).
• Idle Speed: 2,800 rpm.
• Maximum Power Speed: 12,000 rpm.
• Sound Pressure Level: Approx. 105 dB(A).
• Vibration Level (left/right): Approx. 4.5/4.5 m/s².
• Chain Pitch: 3/8" PMM.
• Chain Gauge: 0.043" (1.1 mm).
• Recommended Bar Lengths: 12" to 16".

Controls and Components

Main Controls: Master Control Lever (Stop/Start positions), Throttle Trigger, Throttle Trigger Lockout, Chain Brake Lever, Decompression Valve (if equipped).

Components: Front Hand Guard, Chain Catcher, Muffler, Spark Arrestor Screen, Fuel and Oil Tank Caps, Chain Tensioner Wheel, Bar Stud Nuts.

Operation: Set master control to start position. Pull starter handle briskly. To stop, set master control to STOP (0) position. Chain brake is activated manually (by hand) or automatically by inertia if kickback occurs.

Fuel & Lubrication

Use fresh, clean fuel. STIHL MotoMix® is recommended for optimum performance and shelf life.

1. Fuel Mixing: For 1 US gallon of gasoline (89+ octane), add 2.6 fl oz of STIHL 2-stroke oil. Shake container well.
2. Filling Fuel: Clean area around cap. Use funnel. Do not overfill.
3. Chain Oil: Fill oil tank before each use. Check oil flow by holding saw over light-colored surface and running at full throttle briefly; a line of oil should appear.

Tip: Never use automotive oil, dirty oil, or fuel older than 30 days. Store fuel in an approved container.

Starting & Stopping Procedure

Follow these steps precisely for safe operation.

1. Cold Start: Engage chain brake. Set master control to cold start position (choke). Press decompression valve (if equipped). Place saw on ground, hold front handle with left hand, place right foot in rear handle. Pull starter rope sharply until engine fires (usually 2-5 pulls). Move master control to run position. Pull starter rope again to start.
2. Warm Start: Master control in run position. Engage chain brake. Pull starter rope.
3. Stopping: Release throttle trigger. Let engine idle briefly. Move master control to STOP (0).

WARNING! Always engage the chain brake when starting, carrying, or when the saw is not in immediate use.

Safe Cutting Techniques

Maintain secure footing and grip. Be aware of kickback zone (upper quadrant of bar tip).

1. Bucking (cutting felled logs): Support log off ground. Cut from top. Beware of binding.
2. Limbing: Work from trunk outward. Keep saw stable; do not let tip contact ground.
3. Kickback Prevention: Hold saw firmly with thumbs wrapped. Do not cut with bar tip. Use reduced-kickback chain and bar.
4. Pulling/Pushing Chain: Recognize correct cutting direction for top and bottom of bar.

CAUTION! Never operate saw above shoulder height or with one hand. Plan escape path from falling wood.

Maintenance Schedule

Daily/Before Use: Check chain tension, sharpness, and lubrication. Check for loose fasteners. Clean air intake and saw exterior.

Weekly/Every 10 Hours: Clean spark arrestor screen (if equipped). Check fuel filter. Clean chain brake mechanism.

Monthly/Every 20 Hours: Replace air filter. Check spark plug gap (0.020").

As Needed: Sharpen chain. Replace worn bar. Clean cooling fins.

CAUTION! Disconnect spark plug wire before performing any maintenance other than chain tensioning and lubrication.

Safety & Regulatory Information

This product complies with relevant ANSI/OPEI safety standards. Contains parts that can emit chemicals known to cause cancer. Operate with adequate ventilation. The muffler and engine become extremely hot during use. STIHL and the STIHL logo are registered trademarks of ANDREAS STIHL AG & Co. KG. Quickstop® is a registered trademark. For genuine parts and service, contact an authorized STIHL servicing dealer.

Troubleshooting

Service: For repairs beyond basic maintenance, take your STIHL MS170 to an authorized STIHL servicing dealer.

Support: Find your local dealer at www.stihlusa.com or call 1-800-467-8445.