How to Adjust a Carburetor on a Stihl Chainsaw

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Carburetor adjustment is the process of setting a carburetor to enrich or lean the air/fuel ratio.

Carburetors can be adjusted through the use of an idler screw and needle, located on top of the carburetor.

This allows a user to change the position of the jet inside and affect air/fuel mixture. This can be done manually or through the use of electronic controls, such as the Stihl HT1000.

This article will go over how to adjust a carburetor on a Stihl chainsaw, as well as what not to do.

How to Adjust a Carburetor on a Stihl Chainsaw
Carburetor intake hole

Requirements:

  • Stihl 820 mower or another chainsaw with a carburetor that has an idle adjustment feature.
  • Stihl HT1000 (or other carburetor RPM signal sender) reports the carburetor RPM.
  • A manual throttle stop control (stops the engine from running).

Tools:

  • Dremel with cutting disk(s) or multi-tool.
  • Phillips screwdriver.
  • Socket set or specialized stihl carburetor adjustment tool to remove/install idler screws (hardware store).

Before you get into the list below, watch this video:

CORRECT WAY To Adjust Or Tune The Carburetor On A Chainsaw

Method 1: How to Adjust a Carburetor on a Stihl Chainsaw

  1. Remove the throttle plate to expose the idler screw. Use two fingers, on one hand, to press down on the throttle plate and remove it, exposing the screw.
  2. Press down on the Stihl chainsaw carburetor adjustment screws until it starts to move, allowing griping with one hand. Turn it counterclockwise until you hear a click.
  3. Raise the idler screw into its final position by moving it slightly upward and pressing down again.
  4. Remove the adapter from the carburetor housing and set it aside for re-installation later.

Method 2: Stihl Chainsaw Idle Adjustment

  1. The second method is for carburetors without an idle adjustment feature. The first thing you need to do is remove the throttle plate and air filter housing.
  2. Remove the two screws holding the throttle plate in place, and then remove it by pulling it out of the carburetor housing.
  3. Remove the air filter housing containing the idle jet screw by unscrewing it from the carburetor body with a Phillips head screwdriver, using one hand to hold down on it and one hand to turn clockwise. Now, unscrew the idle jet screw completely.
  4. Remove the idle adjustment adapter from the carb body. Next, use a pair of pliers to loosen and remove the spring from the central shaft.
  5. Remove the idle adjustment screw by unscrewing it counterclockwise until it is fully removed. Remove the washer on top of it and set them aside for re-installation later.
  6. Remove the idler screw and reinstall everything into their respective places.
  7. Replace the idle adjustment adapter, and then install the idle adjustment screw. Make sure it is in the same place it was originally (or run a test drive to make sure).
  8. Replace the air filter housing, and throttle plate, and then reinsert both screws from before. Tighten them in a clockwise direction until they are fully tightened (which may take some force).

You can now test your chainsaw with the new settings. Make sure to keep the throttle plate in the fully open position for testing. The goal is to get the RPMs at or near the setting that the HT1000 requires.

If this is not happening, you can try adjusting further lean or richer if necessary. However, do not adjust more than a few clicks at a time, and do not hold down on the idler screw while turning it. The carburetor can be damaged if this is done.

Method 3:

If you do not have a carburetor RPM signal sender or the carburetor’s idle adjustment monitor is somehow damaged or missing, you can use a throttle stop control. The stop control prevents the engine from running if it is in the process of taking apart. Using this method requires a few extra steps.

  1. First, disconnect and remove the throttle cable from the throttle plate. Then disconnect and remove the air filter housing from the carburetor body.
  2. Next, you want to take out the throttle stop control and put that somewhere safe.
  3. Now it’s time to remove the idle adjustment adapter from the carburetor. You can do this by removing one screw first, then unscrew the two other screws at the end of the adapter. When you are finished, carefully remove it and set it aside.
  4. Now, reconnect and install everything into their respective places. Re-install both screws holding on the air filter housing and throttle plate if they were previously removed. Tighten these in a clockwise direction until they are fully tightened (which may take some force).

You can now test your chainsaw with the new settings. Make sure to keep the throttle plate in the fully open position for testing. The goal is to get the RPMs at or near the setting that the HT1000 requires.

If this is not happening, you can try adjusting further lean or richer if necessary. However, do not adjust more than a few clicks at a time, and do not hold down on the idle screw while turning it. The carburetor can be damaged if this is done.

Method 4:

If you have another type of throttle control setup, you can still use a throttle stop control to perform the adjustments.

  1. First, disconnect and remove the throttle cable from the throttle plate. Then disconnect and remove the air filter housing from the carburetor body.
  2. Next, you want to take out the throttle stop control and put that somewhere safe.
  3. Now it’s time to remove the idle adjustment adapter from the carburetor. You can do this by removing one screw first, then unscrew the two other screws at the end of the adapter. When you are finished, carefully remove it and set it aside.
  4. Now, reconnect and install everything into their respective places. Re-install both screws holding on the air filter housing and throttle plate if they were previously removed. Tighten these in a clockwise direction until they are fully tightened (which may take some force).

You can now test your chainsaw with the new settings. Make sure to keep the throttle plate in the fully open position for testing. The goal is to get the RPMs at or near the setting that the HT1000 requires.

Summary

Now that you have successfully installed the HT1000, are you ready to start using your chainsaw with an easier, more precise throttle response? Just remember to keep the throttle at 25% or less after the blades stop turning on idle.

This is important to prevent over-revving and damaging the engine. Also, be sure to keep the throttle plate in your chainsaw fully open if you want it at a higher RPM.

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