Stihl MS 170 Chainsaw

Safety

The Stihl MS 170 is a light chainsaw, but the chain speed and kickback forces still require full protective practice. Fit the 14″ or 16″ bar only with the specified low-profile chain, keep both hands on the handles, and work from stable footing with a clear escape route. Do not cut above shoulder height or operate one-handed. Use fresh two-stroke fuel mixed at 50:1, and never run the saw indoors or near dry fuel spills.

• Wear chainsaw chaps, eye and face protection, hearing protection, gloves, and cut-resistant boots.
• Confirm the chain brake snaps forward and releases before every start.
• Keep bystanders, pets, and loose brush outside the cutting area.
• Stop the engine before carrying, fueling, tensioning, or clearing a jam.

Unboxing & first run

Inspect the powerhead, guide bar, chain, scabbard, scrench, and paperwork before adding fuel or oil. The MS 170 powerhead is about 9.5 lb, with a 30.1 cc engine rated at 1.3 kW / 1.7 HP. Install the bar and chain, set the chain tension cold, and fill the bar-oil reservoir before filling the 8.5 fl oz fuel tank. Use clean, ethanol-limited gasoline when possible and quality two-stroke oil at 50:1.

• Mount the chain with cutters facing forward on the top run.
• Tighten bar nuts evenly; do not use an impact driver.
• Prime, set full choke for a cold start, and start on firm ground.
• Let the engine warm briefly, then test idle: the chain must not creep.
• Make first cuts in clean wood, avoiding dirt, nails, and stone.

Controls layout

The control layout is compact and easy to read with gloves. The front hand guard is the chain brake lever; pushing it forward locks the chain, pulling it back resets the brake. The rear handle carries the throttle trigger and throttle lockout. The master control lever combines stop, run, choke, and starting positions. Fuel and bar-oil caps sit on the left side of the powerhead, while the side cover retains the clutch, bar studs, and chain-tension adjuster.

• Front handle: left-hand grip and brake activation zone.
• Rear handle: throttle trigger, lockout, and main control access.
• Side cover: bar nuts, sprocket area, chain catcher, and tension screw.
• Bar and chain: 14″ or 16″ setup using 3/8″ Picco Micro (LP), .050 gauge.
• Vibration system: rubber elements at the bar and rear handle reduce hand fatigue but do not replace proper grip.

Routine maintenance

Routine service keeps the small engine easy to start and prevents premature bar, sprocket, and chain wear. Work with the engine off, spark plug lead disconnected for deeper service, and the saw fully cool before removing covers. After every cutting session, brush sawdust from the sprocket cover, bar groove, clutch area, and air intake. Check chain tension often; a warm chain expands, and a loose chain can derail. Use bar oil suited to the temperature, and do not substitute used engine oil.

• Before use: check chain brake, throttle lockout, chain tension, bar oil flow, and fuel leaks.
• After use: clean air filter, bar groove, oil holes, and cooling fins.
• Weekly: inspect starter rope, anti-vibration mounts, chain catcher, and sprocket.
• Spark plug: clean or replace if fouled; typical plug torque is 20 N·m unless the plug maker specifies otherwise.

Blade or chain replacement

Replace the chain when cutters are damaged, tie straps are cracked, rivets are loose, or sharpening has reached the service marks. Replace the bar if rails are spread, the nose sprocket binds, or the groove no longer holds the drive links upright. The MS 170 commonly uses a 14″ bar with 50DL or a 16″ bar with 55DL; confirm the count stamped on the bar before ordering.

• Engage the chain brake, stop the engine, and let the muffler cool.
• Remove the clutch cover and loosen the tensioner until the chain lifts free.
• Clean the bar groove and oil ports before installing the new loop.
• Fit cutters forward on the top run, seat drive links fully, then tension cold.
• Tighten bar nuts while lifting the bar nose, then recheck after one minute of running.

Sharpening or cleaning

A sharp low-profile chain should feed with light pressure and produce chips, not dust. Sharpen before the chain overheats, pulls sideways, or needs force to cut. File every cutter to the same length and angle so the saw tracks straight. The 3/8″ Picco Micro (LP), .050 gauge chain uses low-kickback geometry; do not grind depth gauges aggressively or mix cutter patterns. Clean resin with a chain-safe solvent and dry the loop before oiling.

• Clamp the bar or secure the chain in a filing vise.
• File from inside to outside, holding the file level and consistent.
• Count strokes per cutter; use the shortest cutter as the reference.
• Check depth gauges after two or three sharpenings, using the correct gauge tool.
• Flip the bar periodically to even rail wear, then clear the oil hole.

Troubleshooting

Most MS 170 faults trace to fuel age, air restriction, chain tension, or a dirty cutting system. Diagnose with the saw cool, on level ground, and with the chain brake engaged. If the engine was flooded, move the control to run, hold the throttle open, and pull until it clears; avoid repeated choking. If the saw starts but stalls under load, stop cutting and inspect the chain before adjusting the carburetor.

• Will not start: replace stale 50:1 fuel, check the stop position, inspect spark plug, and clean the air filter.
• Chain does not oil: refill bar oil, clean the bar hole, and check for sawdust packed behind the cover.
• Chain creeps at idle: stop use and correct idle speed or clutch drag.
• Cuts crooked: sharpen evenly, inspect bar rails, and verify chain gauge.
• Excess vibration: inspect rubber mounts, bar nuts, sprocket, and chain damage.

Compatible parts

Use parts that match bar length, chain pitch, gauge, and drive-link count. A chain that is one drive link short will not mount; a chain that is too long may derail even when tensioned. The MS 170 spec here is 3/8″ Picco Micro (LP), .050 gauge, with 50DL for a 14″ bar and 55DL for a 16″ bar. Confirm the bar stamp and sprocket type before replacing parts on an older saw.

• AP—16CB—LP: compatible 16″ low-profile guide bar for this class.
• AP—91PX—55: 16″ low-profile chain loop, 55DL, .050 gauge.
• AP—AF—MS170: air filter service replacement for the MS 170.
• AP—SP—STIHL34: spark plug compatible with the listed Stihl homeowner saws.

Keep a spare chain, plug, air filter, bar oil, and mixed fuel on hand for storm cleanup or remote work.