STIHL M170 Manual

The STIHL M170 is a lightweight, easy-to-use gasoline-powered lawn mower designed for residential use. It features a 4-stroke engine, adjustable cutting height, ergonomic handles, a grass collection bag, and safety features like a blade brake clutch. Below are key sections for safety, features, assembly, operation, maintenance, and troubleshooting.

Features at a Glance

Key components: 4-stroke engine, cutting deck, adjustable handle, grass collection bag, rear roller, and safety key.

Feature	Description
Engine Type	4-stroke, single-cylinder gasoline engine
Cutting Width	16 inches (40 cm)
Cutting Height Adjustment	Central lever with 5 positions
Starter System	Recoil starter with Easy2Start™ technology
Grass Collection	Fabric bag with 1.3 bushel capacity
Safety Features	Blade brake clutch, safety key, dead man's control
Weight	Approximately 20 lbs (9 kg)
Warranty	2-year limited warranty

Assembly Instructions

Unpack all parts and inspect for damage. Assembly requires basic tools (included).

1. Attach the handle: Align handle brackets with deck mounts, secure with provided bolts and wrenches.
2. Install the grass collection bag: Hook bag onto rear brackets, ensure secure fit.
3. Adjust handle height: Loosen knobs, set to comfortable position, retighten.
4. Check wheel alignment: Ensure all four wheels rotate freely.

WARNING! Do not attempt to start the engine before completing assembly. Keep hands clear of cutting blade.

First-Time Operation

Before first use, add fuel and oil, then start the engine following safety procedures.

1. Add engine oil: Use SAE 30 or 10W-30, fill to upper mark on dipstick.
2. Add fuel: Use fresh unleaded gasoline (min. 89 octane), fill tank to 80% capacity.
3. Insert safety key: Push key into slot near handle.
4. Start engine: Set throttle to start position, pull starter cord firmly.
5. Begin mowing: Engage blade control, walk at steady pace.

CAUTION! Operate only in well-ventilated areas. Keep children and pets away during use.

Specifications

• Engine: 4-stroke, 127 cc displacement.
• Power Output: 2.5 kW (3.4 hp) at 3000 rpm.
• Cutting System: Single blade, mulching capability.
• Cutting Heights: 1.2 to 3.1 inches (30-80 mm) in 5 steps.
• Fuel Tank Capacity: 0.53 US gallons (2.0 liters).
• Oil Capacity: 0.42 US quarts (0.4 liters).
• Sound Pressure Level: 92 dB(A) at operator's ear.
• Vibration Level: < 2.5 m/s² (front/rear handles).

Controls and Settings

Main controls located on handle: throttle lever, blade control, cutting height adjuster.

Handle Controls: Throttle (START, RUN, STOP), blade engagement lever, height adjustment lever, safety key slot.

Operation: Set height before starting. Use throttle to control engine speed. Engage blade only when walking. Release blade control to stop blade within 3 seconds (blade brake clutch).

Fuel and Oil Requirements

Use only recommended fuels and oils to ensure performance and longevity.

1. Fuel: Fresh unleaded gasoline, minimum 89 octane. Do not use ethanol blends above E10.
2. Oil: SAE 30 or 10W-30, API classification SJ or higher. Check level before each use.
3. Mixing: Not required (4-stroke engine). Fuel and oil are separate.

Tip: Add fuel stabilizer if storing more than 30 days. Never use old or contaminated fuel.

Cutting Height Adjustment

Adjust cutting height to match grass conditions and desired lawn appearance.

1. Stop engine and wait for blade to stop completely.
2. Pull height adjustment lever upward and move to desired position (1=lowest, 5=highest).
3. Release lever; ensure it locks into place.
4. Test on small area before mowing entire lawn.

WARNING! Never adjust height while engine is running. Keep hands and feet away from cutting deck.

Maintenance Schedule

Regular maintenance ensures optimal performance and extends mower life.

Interval	Task
Before each use	Check oil level, inspect blade for damage, clear debris
Every 25 hours	Clean air filter, check spark plug
Every 50 hours	Change engine oil, sharpen/replace blade
Every 100 hours	Replace air filter, check drive system
Season end	Drain fuel or add stabilizer, clean thoroughly

Storage Guidelines

Proper storage prevents damage and prepares mower for next season.

1. Clean mower thoroughly, removing all grass and debris.
2. Drain fuel tank or add fuel stabilizer and run engine for 5 minutes.
3. Change engine oil if due.
4. Store in dry, covered area away from moisture and direct sunlight.

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

Safety Information

Read and follow all safety instructions to prevent injury or damage.

• Always wear sturdy shoes and eye protection.
• Keep children and pets at least 50 feet away during operation.
• Never operate on slopes greater than 20 degrees.
• Always push mower forward; never pull backward while blade is engaged.
• Inspect area for stones, sticks, and other objects before mowing.
• Use only original STIHL replacement parts.

Troubleshooting

Symptom	Possible Cause	Corrective Action
Engine won't start	Empty fuel tank, old fuel, safety key not inserted	Add fresh fuel, insert safety key, check spark plug
Engine runs poorly	Dirty air filter, contaminated fuel	Clean/replace air filter, drain and refill with fresh fuel
Uneven cutting	Dull blade, incorrect cutting height	Sharpen or replace blade, adjust cutting height evenly
Excessive vibration	Damaged or unbalanced blade	Stop immediately, inspect and replace blade if damaged
Grass not collecting	Full bag, clogged discharge chute	Empty collection bag, clean chute and deck

Service: For repairs not covered in manual, contact authorized STIHL dealer.

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