STIHL MS170 Chainsaw Parts Manual

The STIHL MS170 is a lightweight, easy-to-use chainsaw designed for occasional users and homeowners. This parts manual provides detailed diagrams and part numbers for the complete assembly, including the engine, cutting attachment, fuel system, ignition, and housing components. Below are key sections for safety, parts identification, ordering, assembly diagrams, and maintenance.

1. Parts Overview 2. Engine Assembly Parts 3. Cutting Attachment Parts 4. Fuel & Ignition System Parts 5. Housing & Handle Parts 6. Parts Ordering Information 7. Assembly & Disassembly Notes 8. Maintenance Parts 9. Safety Parts & Guards 10. Warranty & Support 11. Troubleshooting Parts Reference

Parts Overview

Key assemblies: Engine (Cylinder, Piston, Crankshaft), Cutting Attachment (Guide Bar, Saw Chain, Sprocket), Fuel System (Tank, Carburetor, Filter), Ignition (Spark Plug, Module), Housing (Crankcase, Handles), and Safety Components.

Assembly Group	Description
Engine Assembly	Cylinder, piston, crankshaft, bearings, seals
Cutting Attachment	Guide bar, saw chain, drive sprocket, chain tensioner
Fuel System	Fuel tank, carburetor, fuel filter, fuel lines
Ignition System	Spark plug, ignition module, stop switch, wiring
Air Filter System	Air filter cover, filter element, pre-cleaner
Starter Assembly	Starter pulley, rope, handle, spring
Clutch & Sprocket	Centrifugal clutch, drum, needle bearing
Housing & Handles	Crankcase halves, front/rear handles, antivibration elements
Safety Components	Chain brake, hand guard, throttle lockout, chain catcher
Fasteners & Hardware	Screws, nuts, washers, clips, pins

Engine Assembly Parts

Includes all internal combustion engine components.

Cylinder: Part # 1120 020 2001 – With fins and exhaust port.
Piston: Part # 1120 030 2000 – Includes piston rings and wrist pin.
Crankshaft: Part # 1120 040 2001 – With integrated counterweights.
Crankcase: Part # 1120 050 2002 (left), 1120 050 2003 (right).
Bearings & Seals: Main bearings (6202 C3), crankshaft seals.

WARNING! Engine parts require proper torque and assembly. Use genuine STIHL parts only.

Cutting Attachment Parts

Components for cutting wood: guide bar, chain, sprocket.

Guide Bar: Part # 3003 000 3901 (12-inch) or 3003 000 3902 (14-inch).
Saw Chain: Part # 3635 005 0055 (3/8" PMM3, 52 drive links).
Drive Sprocket: Part # 1125 640 2000 – Rim sprocket, 7-tooth.
Chain Tensioner: Part # 1128 650 2000 – Includes screw and adjuster.
Bar Nuts & Cover: Part # 1128 656 2000 (clutch cover).

CAUTION! Always match chain pitch/gauge to bar. Inspect for wear regularly.

Fuel & Ignition System Parts

Fuel Tank: Part # 1120 350 2001 – With integrated filler neck.
Carburetor: Part # 1128 120 0601 – Zama C1Q-S267.
Fuel Filter: Part # 0000 350 3501 – In-tank filter.
Fuel Lines: Part # 1128 358 2000 (supply), 1128 358 2001 (return).
Spark Plug: Part # 0000 400 1305 – Bosch WSR6F or equivalent.
Ignition Module: Part # 1128 400 2001 – Electronic, with stop switch leads.

Housing & Handle Parts

External covers, handles, and antivibration elements.

Front Handle: Part # 1128 790 2000 – With throttle trigger and lockout.
Rear Handle: Part # 1128 791 2000 – With fuel tank interface.
Crankcase Half: Left (1120 050 2002), Right (1120 050 2003).
Antivibration Elements: Part # 1128 796 2000 (set of 4).
Air Filter Cover: Part # 1128 870 2000 – Latches and snorkel.

Parts Ordering Information

Use genuine STIHL parts for safety and performance.

Locate part number from diagrams in this manual.
Contact authorized STIHL dealer with part number and serial number.
Verify compatibility with MS170 model (serial number prefix 114xxxxxx+).

Tip: Keep serial number label (on rear handle) for reference when ordering.

Assembly & Disassembly Notes

Supports repair and replacement procedures.

Disconnect spark plug wire before any work.
Use STIHL special tools where specified (e.g., piston stop, clutch tool).
Torque fasteners to specification (clutch cover nuts: 8-10 Nm).
Apply thread locker to critical screws (cylinder base).
Lubricate bearings and seals with two-stroke oil during assembly.
Align timing marks on crankshaft and piston.
Check chain tension after reassembly.
Test run without chain to verify engine operation.

WARNING! Improper assembly can cause injury or damage. Follow service manual procedures.

Maintenance Parts

Common wear items for regular maintenance.

Air Filter: Part # 0000 350 2501 – Foam element.
Spark Plug: Part # 0000 400 1305.
Fuel Filter: Part # 0000 350 3501.
Chain Sprocket: Part # 1125 640 2000 (replace with chain).
Guide Bar Tip Sprocket: Service kit # 1128 656 2001.
Clutch Drum/Bearing: Part # 1125 656 2000.

Safety Parts & Guards

Critical safety components must be in good condition.

Chain Brake Band: Part # 1128 790 2001.
Hand Guard: Part # 1128 790 2002.
Throttle Lockout: Part # 1128 792 2000.
Chain Catcher: Part # 1128 656 2002.
Right Hand Guard: Part # 1128 791 2001.

Warranty & Support

STIHL Limited Warranty applies to original purchaser. Parts must be installed by authorized dealer for warranty coverage. Copyright © STIHL Incorporated. All trademarks owned by STIHL. For parts diagrams, visit www.stihlusa.com or contact your local STIHL dealer. Customer support: 1-800-467-8445.

Troubleshooting Parts Reference

Symptom	Possible Faulty Part	Part Number/Check
Engine won't start	Spark plug, fuel filter, ignition module	Replace 0000 400 1305; check 0000 350 3501; test 1128 400 2001.
Chain doesn't turn	Clutch, sprocket, drive spring	Inspect 1125 640 2000; replace clutch assembly 1125 656 2000.
Excessive vibration	Antivibration mounts, crankshaft balance	Replace mounts 1128 796 2000; check crankshaft 1120 040 2001.
Fuel leak	Fuel lines, tank seal, carburetor gasket	Replace lines 1128 358 2000/2001; check tank 1120 350 2001.
Chain brake not engaging	Brake band, handle mechanism	Replace band 1128 790 2001; inspect hand guard linkage.

Note: Always disconnect spark plug before troubleshooting. Refer to full service manual for diagnostics.

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