How to Adjust a Carburetor in a Craftsman

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Adjusting the carburetor on a lawnmower is a simple maintenance chore.
Adjusting the carburetor on a lawnmower is a simple maintenance chore. (Image: Steve Mason/Photodisc/Getty Images)

The arrival of spring means it's time for tuning up lawn equipment of all kinds. Some maintenance tasks go beyond the basic, though, and the day may come that every lawn tool with a gasoline-powered engine will need to have the carburetor adjusted or cleaned. On Craftsman equipment with a Tecumseh or Briggs and Stratton carburetor, an adjustment is a simple procedure that requires small adjustments to screws on the carburetor.

Locate the carburetor on your Craftsman equipment. The carburetor is attached to the air filter and a fuel line, and it is generally located on the left side of the engine. The exact location will vary depending on whether you have a riding mower or a push mower, a snow blower or a weed eater. Look for an oval, metal tube mounted on top of a plastic or metal bowl.

Turn the main mixture and idle mixture screws on the carburetor counterclockwise about one full turn with a flat-head screwdriver. Turn the idle speed screw counterclockwise one to two turns beyond where the screw contacts the throttle plate. The idle speed and idle mixture adjustment screws are next to each other on the side of the carburetor; the main mixture adjustment is on top.

Start the engine with the transmission in neutral and let it run for several minutes. Set the engine throttle control for the maximum rpm and very slowly rotate the main mixture screw counterclockwise until the engine begins to sputter and die.

Rotate the throttle control screw clockwise until the engine begins to sputter. Note the number of turns between the two throttle settings that cause the engine to die. The optimal setting is between these – turn the screw to the mid-range. Wait a few seconds for the adjustment to take effect and readjust if the engine does not run smoothly.

Repeat the procedure for the idle mixture screw and idle speed screw with the throttle set to a slow or idle speed. Adjust the screws to mid-range using the procedure described in Step 4.

Take your equipment for a test run. Test it at idle and again with the engine performing its task, whether mowing or blowing leaves. If the engine dies or runs roughly, adjust the carburetor screws 1/8-turn at a time until the equipment runs smoothly at both idle and while doing work.

Tips & Warnings

  • Some newer carburetors on Craftsman equipment are not adjustable and will require a rebuild or replacement.
  • Always be careful when working on running equipment. Make sure blades are not engaged and that someone is nearby in the event of an accident.

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