Stihl MS 170 Parts Manual

The Stihl MS 170 is a lightweight, easy-to-handle chainsaw designed for occasional users and homeowners. This parts manual provides detailed information on the components, assembly, maintenance, and replacement parts for the Stihl MS 170 chainsaw. Below are key sections covering identification, major assemblies, engine components, fuel system, ignition system, cutting equipment, maintenance, and ordering parts.

1. Identification and Specifications 2. Major Assemblies Overview 3. Engine Components 4. Fuel System Parts 5. Ignition System Parts 6. Cutting Equipment and Bar/Chain 7. Air Filtration System 8. Starter Assembly 9. Maintenance and Replacement Intervals 10. Parts Ordering Information 11. Troubleshooting Common Issues

Identification and Specifications

Key identifiers: Model MS 170, serial number location on crankcase. Engine type: Single-cylinder, two-stroke, air-cooled.

SpecificationDescription
Displacement30.1 cc
Power Output1.5 kW (2.0 bhp)
Fuel Tank Capacity250 ml (0.26 US qt)
Oil Tank Capacity145 ml (0.15 US qt)
Weight (Powerhead)3.9 kg (8.6 lbs)
Guide Bar Lengths30 cm (12"), 35 cm (14"), 40 cm (16")
Chain Pitch3/8" PMM3
Spark PlugBosch WSR6F or equivalent
Ignition SystemElectronic, capacitor discharge
Fuel/Oil Ratio50:1 (STIHL HP Ultra or equivalent)

Major Assemblies Overview

Main assemblies: Engine unit, fuel tank, oil tank, handle system, chain brake, clutch, guide bar, and cutting chain.

  1. Engine Unit: Includes cylinder, piston, crankshaft, carburetor, and ignition module.
  2. Fuel/Oil Tank Assembly: Integrated plastic housing containing separate compartments.
  3. Handle System: Front and rear handles with anti-vibration elements.
  4. Chain Brake: Hand guard activates brake band via inertia.
  5. Clutch: Centrifugal clutch engages chain at specific engine RPM.
  6. Cutting Equipment: Guide bar, saw chain, and sprocket.

WARNING! Always disconnect spark plug before disassembling any parts. Use genuine STIHL parts for safety and performance.

Engine Components

Cylinder, piston, crankshaft, connecting rod, bearings, seals, and crankcase.

  1. Cylinder: Aluminum with chrome-plated bore. Part number: 1128 020 1201.
  2. Piston: Single-ring piston with circlips. Part number: 1128 030 2000.
  3. Crankshaft: Includes main bearings and seals. Part number: 1128 040 0800.
  4. Crankcase: Two-piece design. Part number: 1128 010 1200 (complete).
  5. Muffler: Spark-arresting muffler with heat shield. Part number: 1128 140 0601.

CAUTION! Ensure proper torque specifications when assembling engine components. Refer to service manual for values.

Fuel System Parts

Ignition System Parts

Ignition module, spark plug, stop switch, wiring harness.

Ignition Module: Electronic CDI unit. Part number: 1128 400 1305. Spark Plug: Bosch WSR6F or Champion RCJ6Y. Stop Switch: Part number: 1128 960 1000. Wiring Harness: Includes leads to coil and switch. Part number: 1128 960 1201.

Testing: Use STIHL ignition tester or multimeter to check coil resistance (primary: 0.18-0.27 Ω, secondary: 4.7-7.2 kΩ).

Cutting Equipment and Bar/Chain

Guide bar, saw chain, drive sprocket, clutch drum, bar nuts, and chain tensioner.

  1. Guide Bar: Rollomatic E mini 30cm (12"). Part number: 3003 000 3901.
  2. Saw Chain: 3/8" PMM3, 52 drive links. Part number: 3613 005 2052.
  3. Drive Sprocket: Spur sprocket. Part number: 1128 640 2001.
  4. Clutch Drum: Part number: 1128 640 0800.
  5. Chain Tensioner: Screw-type adjuster. Part number: 1128 680 2000.
  6. Bar Nuts: M8 flange nuts. Part number: 0000 957 1003.

Tip: Regularly check chain sharpness and tension. Replace chain when cutters are worn below 4mm.

Air Filtration System

Two-stage air filter: pre-filter and main foam element.

  1. Remove filter cover: Turn knob counterclockwise.
  2. Pre-filter: Remove and clean with compressed air or wash in soapy water.
  3. Main Filter: Foam element. Clean in warm, soapy water, dry, and oil with STIHL filter oil.
  4. Reinstall: Ensure filter is seated properly before replacing cover.

WARNING! Never operate saw without air filter. Dirt ingestion causes rapid engine wear.

Starter Assembly

Starter housing, rope, pulley, spring, and pawls.

Parts: Starter housing (1128 790 1200), starter rope (1128 790 2101), rewind spring (1128 790 2800), pulley (1128 790 2400), pawls (1128 790 2601).

Replacement: Wind spring carefully; ensure rope is properly anchored and pawls engage flywheel.

Maintenance and Replacement Intervals

Daily: Check chain tension, sharpness, lubrication. Clean air filter. Weekly: Clean saw, check all fasteners. 50 hours: Replace spark plug, clean spark arrestor screen. 100 hours: Replace fuel filter, inspect fuel lines. Annual: Replace air filter, check clutch and sprocket wear.

CAUTION! Use only STIHL-approved oils and fuels. Improper mixtures cause engine damage.

Parts Ordering Information

Always provide model number (MS 170) and serial number when ordering parts. Use genuine STIHL parts for warranty compliance and safety. Contact authorized STIHL dealers or visit www.stihlusa.com for parts diagrams and ordering.

Note: Some parts may be sold in kits (e.g., gasket set, seal kit).

Troubleshooting Common Issues

SymptomPossible CauseCorrective Action
Engine won't startFuel, spark, compressionCheck fuel freshness, spark plug, fuel filter, carburetor settings.
Engine runs poorlyClogged filter, carb adjustmentClean air filter; adjust L and H screws per manual.
Chain doesn't turnClutch, sprocket, brakeCheck clutch springs, sprocket wear, ensure brake is disengaged.
Excessive vibrationLoose parts, unbalanced chainTighten all fasteners; check chain for damage and proper tension.
Oil not lubricatingOil pump, passages, bar grooveCheck oil pump function, clean oil passages, ensure bar groove is clear.

Service: For complex repairs, contact authorized STIHL service dealer. Refer to official STIHL service manual for detailed procedures.

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