How To Start A Stihl 170 Chainsaw: The Complete Step-by-Step Operator Guide

Mastering how to start a Stihl MS 170 chainsaw requires a precise sequence of fuel priming, master control lever manipulation, and pull-cord technique to prevent engine flooding. Following the correct cold-start and warm-start protocols ensures reliable ignition, protects the recoil starter mechanism, and extends the overall service life of your 30.1 cc two-stroke engine.

Pre-Operation & Safety Preparation Checklist

Before attempting to fire up your Stihl MS 170, proper preparation ensures both personal safety and optimal mechanical performance. The Stihl MS 170 is a lightweight, compact homeowner saw featuring an 1.8 bhp engine, making it exceptionally popular for property maintenance, firewood cutting, and limb clearing. However, failing to respect its fuel mixture requirements or safety interlocks can lead to difficult starts or equipment damage.

• Essential Gear, Tools & Materials:

  
  
  
  • Fresh two-stroke fuel mixture (50:1 ratio using 89+ octane gasoline and high-quality Stihl two-stroke air-cooled engine oil).
  • High-grade bio-degradable bar and chain oil.
  • Personal Protective Equipment: ANSI-rated safety glasses, chainsaw chaps, heavy-duty work gloves, steel-toe boots, and hearing protection.
  • A clean, flat outdoor staging area free of loose debris and at least 10 feet away from your fuel mixing station.

• Prerequisite Knowledge & Standards:

  
  
  
  • Understand the chain brake mechanism (always engage the front hand guard before starting).
  • Verify that the chain is properly tensioned—it should snap back into the guide bar groove when pulled manually, with zero sag along the bottom edge.
  • Familiarize yourself with the Master Control Lever positions (Cold Start, Run, Stop).

• Execution Benchmarks:

  
  
  
  • Estimated setup and starting duration: 3 to 5 minutes.
  • Operating environment: Well-ventilated outdoor spaces only; never operate a two-stroke engine in an enclosed garage or shed due to carbon monoxide accumulation.

Step-by-Step Starting Procedure for the Stihl MS 170

Step 1: Secure the Chainsaw and Engage the Chain Brake

Place the Stihl MS 170 on a firm, flat piece of ground. Ensure the guide bar and chain are completely clear of dirt, stones, and any objects. Push the front hand guard forward toward the nose of the guide bar to positively engage the chain brake. When engaged, the chain is mechanically locked and cannot rotate, preventing accidental movement during the startup pulls.

Warning: Never attempt a "drop start" where you hold the saw by the top handle and yank the starter cord with one hand. This dangerous practice violates core safety standards, strips recoil assemblies, and leaves the operator with zero control over the running saw.

Step 2: Prepare the Fuel and Check Fluid Levels

Remove the fuel filler cap and chain oil filler cap to verify fluid levels. The MS 170 utilizes a translucent fuel tank allowing visual inspection of your 50:1 mix. Fill both reservoirs if necessary, wiping away any spilled fuel with a clean rag before proceeding. A properly filled bar oil reservoir is critical; running the saw without bar oil will instantly destroy the sprocket, guide bar, and saw chain.

Step 3: Set the Master Control Lever to Full Choke

Locate the black Master Control Lever on the rear handle. To perform a cold start on a completely cold engine, press the lever down fully through the detents into the bottom Full Choke position (often represented by a closed choke valve icon). On newer MS 170 models, moving the lever to this lowest position also automatically sets fast idle to help the engine catch.

Step 4: Prime the Carburetor (If Equipped)

If your specific production run of the Stihl MS 170 features a manual fuel purge bulb (primer bulb), press it firmly and release it 5 to 7 times in succession until you visibly see fuel filling the clear bulb interior. This step draws fuel directly from the tank into the carburetor metering chamber, dramatically reducing the number of pulls required to turn over a cold engine.

Step 5: Execute the Starter Cord Pulls

Place your right foot firmly inside the rear handle base (or straddle the rear handle securely if your boot size permits) to anchor the saw against the ground. Place your left hand firmly around the wrap-around front handlebar. Grasp the starter grip with your right hand and pull the cord slowly straight outward until you feel distinct resistance as the piston reaches top dead center.

Pro-Tip: Do not pull the starter rope out to its absolute maximum physical limit or allow it to snap back loosely against the fan housing; always guide the handle back smoothly to protect the starter pawls and recoil spring.

Give the starter rope a sharp, controlled, vertical pull. Continue this pulling motion until the engine gives a brief "kick" or "pop" sound—this indicates that the engine has fired momentarily and exhausted the initial fuel charge.

Step 6: Transition to Half-Choke / Fast Idle

As soon as you hear that initial engine "pop," immediately move the Master Control Lever up one notch into the Half-Choke or warm-start position. Do not leave the saw in full choke, or subsequent pulls will flood the combustion chamber with excess liquid fuel.

Step 7: Start the Engine and Disengage the Brake

With the lever in the half-choke position, pull the starter grip firmly once more. The engine should start up and run at a fast idle. Quickly blip the throttle trigger with your right index finger; this mechanical action automatically trips the Master Control Lever upward into the standard run position, dropping the engine down to a stable idle speed.

Before lifting the saw off the ground, firmly pull the front hand guard back toward your body to disengage the chain brake. You are now ready to cut.

Stihl MS 170 Specifications and Technical Parameters

Common Starting Failures and Field Fixes

Even with proper technique, small-engine anomalies can occur. Recognizing these failure modes ensures quick resolution in the field.

• Root Cause: Engine Flooding from Over-Choking

  
  
  
  • Actionable Fix: If you pulled the cord too many times on full choke without moving to half-choke, the spark plug is likely fouled with raw fuel. Set the Master Control Lever to the Stop position, remove the spark plug using your combination wrench, invert the chainsaw, and pull the starter cord 6 to 8 times to clear excess fuel out of the cylinder. Wipe the spark plug dry, reinstall it snugly, set the control lever to Run (not choke), and pull the cord steadily until it fires.

• Root Cause: Stale or Incorrect Fuel Mixture

  
  
  
  • Actionable Fix: Two-stroke fuel containing ethanol degrades rapidly within 30 days, absorbing ambient moisture and gumming up tiny carburetor jets. Drain the old fuel tank completely, flush with a small amount of fresh 50:1 mix, and fill with fresh alkylate-based fuel or fresh gasoline treated with a fuel stabilizer.

• Root Cause: Clogged Spark Arrestor Screen

  
  
  
  • Actionable Fix: Carbon buildup can block exhaust gas flow through the muffler's spark arrestor screen, choking the engine so it refuses to start or sustain idle. Remove the muffler cover screw, pull out the metal mesh screen, and clean away carbon deposits with a wire brush or burn them off with a propane torch before reinstalling.

Frequently Asked Questions

Why won't my Stihl MS 170 start even with fresh fuel?

If fuel is fresh and the spark plug is dry, the issue usually stems from a lack of spark or air restriction. Inspect the air filter for heavy sawdust clogging, ensure the ignition lead wire is firmly pressed onto the spark plug terminal, and verify the on/off switch is not stuck in the ground position.

How do I restart my Stihl MS 170 when the engine is already warm?

For a warm engine, you do not need to use the choke. Move the Master Control Lever directly to the Run position, ensure the chain brake is engaged, anchor the saw on the ground, and pull the starter cord. The engine should fire within one or two pulls.

What causes the pull cord to feel completely loose or stuck?

A loose starter cord indicates that the starter rope has snapped or the recoil spring and starter pawls have disengaged from the flywheel hub. Conversely, a completely locked cord usually indicates a severe mechanical seizure, hydraulic lock from excessive oil in the cylinder, or a jammed chain brake assembly.

How often should I replace the spark plug on an MS 170?

Under normal residential operating conditions, inspect and clean the spark plug (Bosch WSR 6 F or NGK BPMR 7 A) every 50 hours of operation. Replace the plug annually or whenever electrode gap erosion exceeds 0.5 mm (0.020 inches).

Can I run non-synthetic two-stroke oil in my Stihl chainsaw?

While you can run conventional TC-W3 rated oils in a pinch, Stihl strongly recommends using high-grade fully synthetic two-stroke oils formulated specifically for air-cooled engines at a 50:1 ratio to minimize carbon deposits and prevent premature piston scoring.

Elevate your property maintenance efficiency by keeping your Stihl MS 170 tuned, clean, and fueled with precision-mixed oil. Bookmark this authoritative guide to ensure flawless cold-weather and hot-weather engine starts every single cutting season.