How to Adjust a Husqvarna 51 Carburetor

If your Husqvarna 51 chainsaw is having idling issues, the carburetor may need to be adjusted. The carburetor is where the fuel and air mix before entering the engine cylinder. If the fuel-to-air ratio is wrong or the amount of mixture sent into the cylinder is incorrect, the chainsaw can have trouble starting and stalling when you operate it. There is an idle speed screw and an idle mixture screw that can be adjusted on the carburetor to improve the performance of the Husqvarna 51 if these problems occur.


Clean the air filter before adjusting the carburetor. A dirty air filter can affect the adjustments you make to the carburetor.

  1. Locate the idle-speed screw and the idle-mixture screws on the side of the chainsaw. According to the manual for the Husqvarna 51 available at ManualsLib, the idle-speed screw is labeled "T," the low-speed screw is labeled "L" and the high-speed screw is labeled "H."

  2. Turn both the low- and high-speed screws clockwise to the midpoint. Do not turn the screws beyond the stop points or engine damage may occur. Start the saw and let it run for a few minutes. If the chain rotates while idling, turn the "T" idle-speed screw counterclockwise until the chain stops. Madsen's Shop & Supply Inc. recommends checking the engine speed with a tachometer. It should be around 2,700 rpm.

  3. Adjust the low-idle screw clockwise and counterclockwise respectively, until you find the highest idling speed. Adjust the "T" idle screw again if the chain begins to rotate. The carburetor has been correctly adjusted when the saw accelerates without hesitation, and it idles smoothly.

  4. Adjust the idle high-speed screw "H" to increase or decrease the power of the saw. Turning it clockwise increases power, and counterclockwise decreases power. Don't set it too high or it can damage the engine. However, setting it too low won't give the saw sufficient power to operate. Find the ideal setting by adjusting it clockwise and counterclockwise. Check the acceleration and idle of the chainsaw again to make sure it revs and idles smoothly.

  5. Things You Will Need

    • Flathead screwdriver

    • Tachometer


    If the idle speed cannot be adjusted so that the chain stops, contact a local service center. Do not use the saw if the idle speed is not functioning properly. Service the chainsaw on a flat surface with the bar pointed away from you to prevent the bar and chain from contacting the ground or other objects.