Carburetor adjustment is a crucial aspect of maintaining optimal performance for your STIHL FS120, FS200, FS250, or FS300 brushcutter. A properly adjusted carburetor ensures efficient fuel-to-air mixture, leading to consistent power, reduced emissions, and a longer lifespan for your equipment.

Advertisement

Safety First

Before beginning any maintenance or adjustment, always ensure the following:

  • Turn off the engine: This is a critical safety measure to prevent accidental startup.
  • Allow the engine to cool: A hot engine can cause burns.
  • Wear protective gear: This includes safety glasses, gloves, and appropriate clothing.

Identifying the Carburetor

The carburetor is a small, complex component located on the engine’s side. It typically has a black or silver finish and several adjustment screws.

Tools Needed

  • Phillips screwdriver
  • Flathead screwdriver
  • Wrench (if necessary for removing the air filter cover)

Adjustment Process

  1. Access the carburetor: Remove the air filter cover, if applicable, to expose the carburetor.
  2. Locate the adjustment screws: Most STIHL brushcutters have two adjustment screws:
    • Low-speed screw (L): Controls the fuel-to-air mixture at idle.
    • High-speed screw (H): Controls the fuel-to-air mixture at full throttle.
  3. Start the engine: Follow the manufacturer’s instructions to start the engine.
  4. Warm up the engine: Let the engine run for a few minutes to reach operating temperature.
  5. Adjust the low-speed screw (L):
    • With the engine idling, slowly turn the L screw clockwise until the engine starts to surge or die.
    • Then, turn the screw counterclockwise until the engine idles smoothly.
  6. Adjust the high-speed screw (H):
    • Increase the engine’s RPMs to full throttle.
    • Slowly turn the H screw clockwise until the engine starts to surge or lose power.
    • Then, turn the screw counterclockwise until the engine runs smoothly at full throttle.
  7. Fine-tune adjustments: Make small adjustments to the L and H screws until you achieve the desired engine performance.
  8. Test the engine: Run the engine at various speeds and loads to ensure proper operation.

Additional Tips

  • If you’re unsure about carburetor adjustment, consult the owner’s manual or seek professional assistance.
  • A dirty or clogged carburetor can affect performance. Regular cleaning and maintenance are essential.
  • Consider using a carburetor cleaner to remove deposits and restore optimal function.

By following these steps and taking necessary precautions, you can effectively adjust the carburetor on your STIHL FS120, FS200, FS250, or FS300 brushcutter, ensuring reliable and efficient performance.