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Starting a professional-grade Stihl trimmer like the FS 120, 200, or 250 requires a specific sequence to avoid flooding the engine. These robust 2-stroke machines are built to last, but they can be finicky if you don’t follow the “warm” vs “cold” start rules.

Watch the full step-by-step video guide below:

Step 1: Check Your Fuel (50:1 Mix)

Ensure you are using a fresh 50:1 mixture of high-grade gasoline and 2-cycle air-cooled engine oil. Using old fuel is the most common reason these units fail to stay running.

Step 2: Set the Slide Control to “Start”

To move the orange slide control, you must first squeeze the Throttle Trigger and the Trigger Interlock (the lever on top of the handle) at the same time. While holding them down, slide the switch to the START position and release the triggers. This “locks” the throttle in the correct position for a fast start.

Step 3: Prime the Carburetor

Press the manual fuel pump bulb (the primer bulb) at least five times. Even if the bulb is already full of fuel, this clears air out of the system and ensures fresh gas is in the carb.

Step 4: Set the Choke for a Cold Start

If the engine is cold, turn the choke knob to the Full Choke position (represented by the closed flap icon). If the engine is already warm from recent use, skip this and move to the “Run” position.

Step 5: Pull the Starter Cord (Listen for the “Burp”)

With the trimmer on the ground, pull the starter rope firmly. Listen closely: After 2–3 pulls, the engine should make a brief “popping” or “coughing” sound. This is the “burp.” Stop pulling immediately when you hear it.

Step 6: Move to Run and Finish Starting

Turn the choke knob to the Run/Open position. Pull the starter rope again. The engine should fire up and stay running within 1–2 pulls.

Note: Pulling more than twice on full choke after the “burp” will flood the engine.

Step 7: The “Throttle Blip”

Once the engine is running, the trimmer head will be spinning at high speed because of the “Start” lock. Quickly squeeze and release the throttle trigger to return the engine to a safe idle.

How to Restart a Warm Engine

If you have already been using your Stihl FS 120, 200, or 250 and it is still warm to the touch, do not use the choke. Using the choke on a hot engine will cause it to flood instantly.

  1. Set to Start: Move the slide control to the START position.
  2. Leave Choke Off: Ensure the choke knob is in the Run/Open position.
  3. Pull the Cord: Give the starter rope a firm pull. It should fire up in 1–2 pulls without any extra fuel priming.
  4. The Blip: Just like the cold start, squeeze the trigger to release the throttle lock once it’s running.

Troubleshooting: What to do if it won’t start

If you’ve pulled the cord more than 10 times and nothing is happening, you have likely flooded the engine.

  1. Clear the Gas: Move the choke to the Run (Off) position.
  2. Full Throttle: Squeeze the throttle trigger all the way.
  3. Clear the Chamber: While holding the throttle open, pull the starter cord 5–10 times. This forces air into the engine to dry out the spark plug.
  4. Try Again: Once it “pops,” release the trigger and start normally.

Maintenance & Additional Resources

To keep your Stihl FS 120, 200, or 250 running strong for years, follow these quick maintenance tips:

  • Clean the Cooling Fins: Remove the orange shroud and brush away grass to prevent overheating.
  • Check the Spark Plug: If it’s black or oily, replace it with a fresh NGK BPMR7A. 🔗 Check current prices on Amazon.
  • Air Filter Care: Tap out the dust after every 5 hours of use.
  • Official Support: If you need specific torque specs or part numbers, you can view the Official STIHL FS 120, 200, 250 Instruction Manual.

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