How to Adjust the Carb on a Husqvarna 325RX

Updated February 21, 2017

The Husqvarna 325Rx Brushcutter operates with a carb that can be adjusted to control the engine speed. The carburettor on the 325Rx comes set at the factory. However, after a break-in period of at least 10 tanks of gas, the carburettor can be fine tuned to reach peak engine performance. Carburettor adjustment is difficult and, if done poorly, can damage or ruin the engine. For this reason, Husqvarna recommends only a skilled technician adjust the carburettor.

Unscrew the knob on the air filter cover, lift the cover off and take out the air filter pad. Wash the pad in warm soapy water, rinsing it under cool water afterward. Let it sit out for several hours to dry thoroughly. Brush the area around the filter box and cover.

Unscrew the fuel tank cap and pour out fuel that has been in it for more than 72 hours. Fill the 325Rx with freshly mixed fuel. Locate the "H" "L" and "T" holes on the back of the engine. Turn the "H" and "L" screws to their midpoint between fully turned in clockwise and fully turned out counterclockwise.

Start the 325Rx engine and let it run at a high idle for at least 10 minutes before adjusting the carburettor. Insert the small screwdriver into the hole marked "L" for the low speed. Turn the screw clockwise until the engine starts surging, then turn it counterclockwise until the engine starts bubbling.

Fine-tune the screw between these two settings to find the best idle speed. Listen carefully to the sounds of the engine and look for the cleanest, smoothest sound. Move the screw counterclockwise 1/4-turn when the highest idle speed is found to prevent engine damage.

Adjust the idle speed screw marked with a "T" clockwise until the blade starts to rotate. Stop moving it and reverse it slowly until the blade stops spinning. Locate the highest idle speed before the cutting attachment starts moving. Never operate the brush cutter with the head turning while idling.


Leave the high speed screw adjusting to a professional. Engine damage can occur in as little as 10 seconds if the engine runs too fast.

Things You'll Need

  • Brush
  • Warm soapy water
  • Approved fuel container
  • Freshly mixed 325Rx fuel
  • Small screwdriver
Cite this Article A tool to create a citation to reference this article Cite this Article

About the Author

Currently based in Minneapolis, Minn., Eric Blankenburg has been a freelance journalist since 2000. His articles have appeared in "Outside Missoula, Outside Bozeman," "Hello Chengdu" and online at and various other websites. He holds a Bachelor of Arts in creative writing from the University of Montana.