stihl ms170 repair manual pdf

The STIHL MS 170 is a lightweight, easy-to-handle chainsaw designed for occasional users and homeowners. This repair manual covers essential maintenance, troubleshooting, and repair procedures for the MS 170 model, including engine disassembly, fuel system servicing, ignition system checks, chain and bar maintenance, and safety precautions. Below are key sections for specifications, safety, maintenance schedules, troubleshooting, and step-by-step repair instructions.

1. Features and Specifications 2. Safety Information 3. Maintenance Schedule 4. Troubleshooting Guide 5. Engine Repair 6. Fuel System 7. Ignition System 8. Chain and Guide Bar 9. Carburetor Adjustment 10. Assembly/Disassembly 11. Warranty & Support

Features and Specifications

Key components: Engine, Fuel Tank, Chain Brake, Guide Bar, Chain, Air Filter, Spark Plug, Muffler.

FeatureDescription
Engine TypeSTIHL 2-stroke, single-cylinder
Displacement30.1 cc
Power Output1.5 kW (2.0 hp)
Fuel Tank Capacity250 ml (0.25 liters)
Chain Oil Tank Capacity145 ml
Guide Bar Lengths12", 14", 16" (30 cm, 35 cm, 40 cm)
Chain Pitch3/8" PMM3
Weight (without cutting attachment)3.9 kg (8.6 lbs)
Ignition SystemElectronic, capacitor discharge (CDI)
CarburetorSTIHL ZAMA diaphragm carburetor

Safety Information

Always prioritize safety when operating or repairing the chainsaw.

  1. Wear protective equipment: Safety glasses, gloves, hearing protection, chainsaw chaps, and sturdy boots.
  2. Work in a well-ventilated area away from sparks or open flames when servicing.
  3. Disconnect the spark plug boot before performing any repairs to prevent accidental starting.
  4. Use only STIHL-approved replacement parts and lubricants.

WARNING! Fuel is highly flammable. Do not smoke or work near ignition sources. Allow engine to cool before servicing.

Maintenance Schedule

Regular maintenance ensures optimal performance and longevity.

  1. Before each use: Check chain tension, sharpness, and lubrication. Inspect for loose fasteners.
  2. After each use: Clean air filter, check for fuel leaks, wipe down saw.
  3. Every 20 hours: Replace spark plug, clean spark arrestor screen, check fuel filter.
  4. Every 50 hours: Clean carburetor, replace air filter, inspect fuel lines.
  5. Annually: Replace fuel filter, inspect clutch and sprocket, check anti-vibration elements.

CAUTION! Follow torque specifications when tightening fasteners. Over-tightening can damage components.

Specifications

Controls and Settings

Main controls: Throttle Trigger, Throttle Trigger Lockout, Stop Switch, Choke/Start Position Lever, Chain Brake, Master Control Lever.

Adjustments: Chain Tension (via side knob), Carburetor (H, L, LA screws), Idle Speed. Maintenance points: Air Filter Cover, Fuel Cap, Oil Cap, Spark Plug, Muffler Cover.

Carburetor Settings (factory default): L screw - 1 turn open; H screw - 1 turn open; LA (idle) - preset. Final tuning must be performed with warm engine and proper load.

Troubleshooting Guide

Common problems and solutions for the MS 170.

  1. Engine won't start: Check fuel, spark, air filter, choke position.
  2. Engine starts then dies: Clean fuel filter, check fuel lines, adjust carburetor.
  3. Loss of power: Clean air filter, check spark arrestor, examine piston through exhaust port.
  4. Chain doesn't turn: Check clutch, sprocket, chain brake engagement.
  5. Excessive vibration: Inspect anti-vibration mounts, check for loose components.

Tip: Always follow systematic diagnosis: Fuel > Spark > Compression > Air.

Engine Repair

Cylinder, piston, crankshaft, and connecting rod service.

  1. Remove top cover, air filter, carburetor, and muffler.
  2. Remove cylinder bolts and carefully lift cylinder.
  3. Inspect piston and cylinder for scoring, carbon buildup, or damage.
  4. Measure piston clearance (spec: 0.045-0.055 mm).
  5. Replace piston rings if worn or broken (ring end gap: 0.25-0.40 mm).
  6. Clean carbon from exhaust port and combustion chamber.
  7. Reassemble with new gaskets, torquing cylinder bolts to 10 Nm (88 in-lb).

WARNING! Do not damage the crankcase seals during disassembly. Replace if leaking.

Fuel System

Fuel tank, lines, filter, and carburetor service.

Fuel Line Replacement: Drain tank, remove old lines, install new lines with proper routing (primer bulb lines if equipped). Fuel Filter: Replace annually or when clogged. Carburetor Cleaning: Disassemble, soak in carb cleaner, blow out passages with compressed air, install rebuild kit if worn.

Ignition System

Spark plug, ignition module, and flywheel service.

Spark Plug: Check gap, replace if electrode worn. Ignition Module: Check air gap (0.3 mm / 0.012") between flywheel and module poles. Resistance check: Primary 1.5-2.5 Ω, Secondary 8-12 kΩ. Flywheel: Remove with puller, inspect key and keyway, torque nut to 40 Nm (30 ft-lb).

CAUTION! Do not strike flywheel with hammer. Use proper puller to avoid damage.

Chain and Guide Bar

Maintenance, sharpening, and replacement.

  1. Chain Tension: Adjust so chain snaps back when pulled from bar.
  2. Sharpening: Use correct file size (4.0 mm / 5/32" for 3/8" PMM3). Maintain 30° top plate angle, 10° down angle.
  3. Bar Maintenance: Clean groove, flip bar regularly, dress rails with flat file.
  4. Sprocket: Replace if worn (recommended every 2-3 chains).
  5. Chain Brake: Test function, clean band and mechanism, replace if damaged.

WARNING! Always wear gloves when handling chain. Ensure chain brake is functional before use.

Warranty & Support

STIHL Limited Warranty: 1 year consumer, 90 days commercial. Proof of purchase required.

For technical support, genuine parts, and service manuals: Contact authorized STIHL dealers or visit www.stihlusa.com. This repair manual is for reference only. STIHL recommends major repairs be performed by qualified technicians.

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