How to Adjust the Carb on a Tecumseh Engine
- 1). Locate the main mixture screw on the carburetor. On float-style carbs, this screw is on the bottom of the float. On diaphragm-style carbs, it is one of two screws on the side of the carburetor (the main mixture screw is the one on the right, while the idle mixture screw is on the left). Hand-turn the main mixture screw clockwise until it is finger-tight.
- 2). Insert a flat-head screwdriver in the main mixture screw. Turn the screw counterclockwise one-and-a-half turns for float carbs, and one full turn for diaphragm carbs.
- 3). Turn the idle mixture screw by hand clockwise until it is finger-tight. On float carbs, this screw is on the side of the carburetor. On diaphragm carbs, it is one of two screws on the side of the carburetor, to the left of the main mixture screw you adjusted in Step 2.
- 4). Insert the flat-head screwdriver in the idle mixture screw. Turn the screw counterclockwise one full turn for both float and diaphragm carbs.
- 5). Start the engine and let it idle.
- 6). Adjust the idle screw in small increments with a screwdriver until the engine idles smoothly.
- 7). Open the engine to full throttle. Adjust the main mixture screw until the engine runs smoothly under full power.
Source...