stihl ms170 repair manual free download

Tools Required

Basic toolkit: Screwdrivers (flat, Phillips), socket set (8mm, 10mm, 13mm), Torx T27, spark plug wrench, compression gauge, feeler gauges, carburetor adjustment tool.

Specialty Tools (recommended): STIHL piston stop tool, flywheel puller, clutch removal tool, pressure/vacuum tester for crankcase.

Always refer to the specific repair procedure for required tools. Use calibrated torque wrenches for reassembly.

Routine Maintenance

Daily/Pre-Use: Check chain tension, sharpness, and lubrication. Inspect for loose fasteners and damage.

1. Air Filter: Clean weekly (more often in dusty conditions). Remove, tap clean, or wash in soapy water if foam. Dry completely before reinstalling.
2. Spark Plug: Check every 25 operating hours. Clean electrode, adjust gap, or replace if worn.
3. Chain Oil System: Verify oil flow by running saw at idle over light-colored surface; look for oil splatter. Clean oil outlet hole in guide bar.
4. Fuel Filter: Replace annually or if clogged. Use STIHL part #0000 350 3501.

CAUTION! Use only STIHL-approved bar and chain oil. Never use waste oil.

Engine Troubleshooting

Common starting/running problems and solutions.

Fuel System Repair

Carburetor removal and service.

1. Disconnect fuel line and impulse line from carburetor.
2. Remove air filter cover and filter.
3. Remove carburetor mounting nuts/wing nuts.
4. Lift carburetor off intake manifold.
5. Disassemble carburetor (diaphragms, gaskets, needle valve). Clean with carburetor cleaner.
6. Inspect diaphragms for cracks or stiffness. Replace kit if needed (Zama K10-HD6 or Walbro K10-WAT).
7. Reinstall in reverse order. Prime bulb should fill with fuel.

WARNING! Use new gaskets. Ensure all fuel lines are securely connected and not cracked.

Ignition System

Testing and replacing ignition module (coil).

Spark Test: Remove spark plug, reconnect wire, ground plug base to cylinder. Pull starter rope – look for bright blue spark. No spark indicates faulty coil, wire, or stop switch.

1. Remove starter cover and flywheel nut (left-hand thread).
2. Use flywheel puller to remove flywheel.
3. Remove ignition module mounting screws.
4. Replace with STIHL module (part #4140 400 0801). Set air gap to 0.3 mm (0.012") using feeler gauge between coil legs and flywheel magnets.
5. Reinstall flywheel and tighten nut to 40 Nm (30 ft-lb).

Chain & Bar Maintenance

Sharpening, tensioning, and replacement.

1. Tensioning: Loosen bar nuts. Use adjustment screw to tighten chain until snug against bar bottom. Chain should pull freely by hand. Retighten bar nuts.
2. Sharpening: Use round file (4.0 mm / 5/32") at 30° angle. Maintain equal tooth length and file depth gauges (rakers) with flat file.
3. Bar Care: Flip bar monthly for even wear. Clean bar groove and oil holes. Replace if groove is deeply worn or rails are uneven.
4. Chain Replacement: Match pitch (3/8" PMM3) and gauge (0.043" / 1.1 mm). Drive link count must match bar length.

Tip: Always wear heavy gloves when handling the chain.

Clutch & Sprocket

Removal and inspection.

1. Remove bar, chain, and clutch cover.
2. Use STIHL clutch tool (or punch) to hold clutch assembly. Clutch has left-hand threads (turn clockwise to loosen).
3. Inspect clutch shoes for wear and springs for damage.
4. Remove sprocket (drum). Replace if worn (rim sprocket part #1145 640 2003).
5. Reinstall in reverse order. Torque clutch to 40 Nm (30 ft-lb).

CAUTION! The clutch is under spring tension. Wear eye protection during disassembly.

Parts Diagram & List

Key replacement parts for STIHL MS 170.

Disclaimer: This free manual is for informational purposes. Always consult an authorized STIHL service dealer for complex repairs. STIHL is a registered trademark. Diagrams available at STIHL dealer portals.

Support: For genuine parts and service, locate your nearest STIHL dealer at www.stihlusa.com.