MS170 Chainsaw Manual

The MS170 is a lightweight, easy-to-handle chainsaw designed for homeowners and occasional users. It features a reliable 30.1cc gasoline engine, STIHL Quickstop® inertia chain brake, Ematic™ lubrication system, and STIHL anti-vibration system. Below are key sections for safety, features, assembly, operation, maintenance, and troubleshooting.

Features at a Glance

Key components: 30.1cc gasoline engine, 16" guide bar, STIHL Oilomatic® saw chain, side-access chain tensioner, combined choke/stop control, and transparent fuel tank.

Feature	Description
Engine	30.1cc, single-cylinder, 2-stroke gasoline engine
Guide Bar Length	16 inches (standard)
Chain Brake	STIHL Quickstop® inertia-activated chain brake
Lubrication System	Ematic™ system for reduced oil consumption
Anti-Vibration	STIHL anti-vibration system for reduced user fatigue
Fuel Tank Capacity	8.5 fl. oz. (0.25 liters)
Oil Tank Capacity	5.1 fl. oz. (0.15 liters)
Weight (without fuel/oil)	7.9 lbs (3.6 kg)
Ignition System	Electronic ignition (CDI)
Starter	STIHL Easy2Start™ system (optional)

Safety Information

Read and understand all safety warnings before operation.

1. Personal Protective Equipment (PPE): Always wear safety glasses, hearing protection, gloves, chainsaw chaps/pants, and sturdy boots.
2. Work Area Safety: Clear area of bystanders, especially children. Ensure secure footing.
3. Chain Brake Check: Verify chain brake functions before each use by performing a manual test.
4. Kickback Awareness: Understand kickback zone (upper quadrant of bar tip). Never cut with tip.

WARNING! Failure to follow safety instructions can result in serious injury or death. Never operate a chainsaw while tired, under the influence, or in poor weather conditions.

Assembly & Preparation

Assemble the chainsaw following these steps.

1. Attach Guide Bar & Chain: Loosen bar nuts. Place bar on studs. Fit chain over sprocket and onto bar groove, ensuring cutting teeth face forward on top. Tighten bar nuts finger-tight.
2. Tension Chain: Use side-access tensioner screw to adjust until chain fits snug against bar but can be pulled by hand. Retighten bar nuts securely.
3. Fuel Mix: Use STIHL MotoMix® pre-mixed fuel or mix high-quality 2-stroke oil with unleaded gasoline (50:1 ratio). Shake well.
4. Fill Tanks: Add fuel to fuel tank and STIHL chain oil to oil tank. Wipe away spills.

CAUTION! Use only STIHL-approved bar, chain, and lubricants. Incorrect fuel mix can cause engine damage.

Specifications

• Engine Displacement: 30.1 cc (1.84 cu. in.)
• Power Output: 1.5 kW (2.0 bhp)
• Maximum Engine Speed: 13,000 rpm
• Fuel/Oil Ratio: 50:1 (STIHL 2-stroke oil)
• Chain Pitch: 3/8" PMM3
• Chain Gauge: 0.043" (1.1 mm)
• Drive Links: 55 (for 16" bar)
• Sound Pressure Level: 103 dB(A)
• Vibration Levels (front/rear): 4.5/3.5 m/s²
• Warranty: Limited 1-year consumer warranty

Controls and Components

Familiarize yourself with all controls before starting.

Right Side: Throttle trigger, throttle trigger lockout, rear handle, master control lever (choke/run/stop), decompression valve (optional).

Left Side: Front handle with hand guard, chain brake lever, chain tensioner screw, oil filler cap, fuel filler cap.

Master Control Lever Positions: - STOP (0): Engine off. - RUN (I): Normal operation. - CHOKE (⏫): Cold starting.

Chain Brake: Engage manually by pushing hand guard forward. Automatically engages via inertia in kickback event.

Starting & Stopping Procedure

Cold Start:

1. Engage chain brake by pushing hand guard forward.
2. Press decompression valve (if equipped).
3. Set master control lever to CHOKE (⏫).
4. Press fuel primer bulb 5 times (if equipped).
5. Place saw on ground, hold front handle with left hand, place right foot in rear handle.
6. Pull starter handle slowly until engagement, then briskly. After engine fires, move lever to RUN (I).
7. Pull starter again until engine starts. Disengage chain brake.

Warm Start: Set lever to RUN (I) and pull starter.

Stopping: Release throttle, set master control lever to STOP (0).

Operation & Cutting Techniques

Always use proper cutting techniques to maintain control.

1. Felling (Cutting Down a Tree): Plan escape path. Make notch cut (1/3 tree diameter) on fall side. Make felling cut from opposite side, leaving hinge wood.
2. Limbing: Work from trunk base upward. Keep saw close, use guide bar's underside.
3. Bucking (Cutting Logs): Support log. Cut from top, avoid pinching by cutting compression side first.
4. Kickback Prevention: Maintain firm grip, do not overreach. Never cut above shoulder height.

Tip: Let the saw do the work; do not force it. Keep chain sharp and properly tensioned.

Maintenance Schedule

Interval	Task
Before each use	Check chain tension, sharpness, brake function, fuel/oil levels
After each use	Clean air intake, check for loose fasteners, clean saw body
Every 5 hours	Clean spark arrestor screen (if equipped)
Every 20 hours	Clean/replace air filter, check spark plug
Every 50 hours	Replace fuel filter, clean cooling fins
Annually	Professional inspection of clutch, sprocket, anti-vibration elements

CAUTION! Always disconnect spark plug wire before performing maintenance.

Chain Sharpening & Tensioning

A sharp, properly tensioned chain is essential for safety and performance.

1. Tensioning: Loosen bar nuts. Turn tensioning screw clockwise until chain fits snug against bar but pulls freely. Retighten bar nuts (snug, not over-tightened).
2. Sharpening: Use round file matching chain pitch (5/32" for 3/8" PMM3). File each cutter at 30° angle, maintaining original shape. File depth gauges with flat file.
3. Check: Chain should not sag from bar underside. All cutters should be equal length.

WARNING! Wear gloves when handling chain. A loose chain can derail; an over-tightened chain can break.

Storage Guidelines

Proper storage prevents fuel system issues.

1. Drain fuel tank or add fuel stabilizer and run engine for 2 minutes.
2. Run chain oil tank dry to prevent leaks.
3. Clean entire saw, especially cooling fins and air filter.
4. Remove chain, clean in solvent, oil lightly, and store separately.
5. Store in dry, cool place, out of reach of children.

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

Troubleshooting

Symptom	Possible Cause	Corrective Action
Engine will not start	No fuel, flooded, spark plug faulty	Check fuel, set lever to RUN, pull 10x with throttle open. Check/replace spark plug.
Engine starts then dies	Clogged fuel filter, air filter, carburetor	Replace fuel filter. Clean/replace air filter. Have carburetor serviced.
Chain does not turn	Chain brake engaged, clutch worn, sprocket damaged	Disengage chain brake. Inspect clutch and sprocket; replace if worn.
Chain throws oil excessively	Oil pump setting too high	Adjust oil flow screw (counterclockwise to reduce).
Poor cutting performance	Dull chain, incorrect filing, low chain speed	Sharpen chain properly. Check engine speed; have carburetor adjusted if needed.

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

Support: 1-800-467-8445; www.stihlusa.com