How to Adjust the Float Level in a Zenith Stromberg Carburetor

Adjusting the float level is essential for ensuring proper fuel delivery. If the float level is too high, the carburetor may flood. If it's too low, the engine may run lean. Follow these steps to get it right.

Tools Needed:

A ruler or caliper (metric)
Flathead screwdriver
Clean workspace
Float height specification (usually 17mm–19mm depending on model)

Step-by-Step Instructions

1. Remove the Carburetor Top
Unbolt the air piston cover by removing the screws that secure it to the carb body. Carefully lift it off. Watch for the diaphragm—it may be stuck to the cover and is delicate.

2. Invert the Carburetor Top
Turn the top cover upside down so the float is hanging down. The float should rest gently against the needle valve. Do not compress any spring-loaded tip if present.

3. Measure the Float Height
Use a ruler or caliper to measure the distance from the gasket surface (where the top meets the bowl) to the bottom of the float (not the seam). The correct height is usually between 17mm and 19mm, but refer to your carb model’s specifications for accuracy.

4. Adjust the Float
Bend the small metal tang on the float arm that contacts the needle valve:

To raise the fuel level (decrease float height), bend the tang upward.
To lower the fuel level (increase float height), bend the tang downward.
Be careful not to put pressure on the needle or it will leak.

Recheck the measurement after bending to ensure it's within spec.

5. Inspect the Float for Damage
Gently shake the float. If you hear fuel sloshing inside, the float is fuel-logged and must be replaced. Also check for cracks or pinholes.

6. Reassemble the Carburetor
Reinstall the diaphragm carefully, aligning any locator tabs. Replace the top cover and tighten the screws evenly to avoid warping. If the carb was removed from the vehicle, reinstall it and reattach fuel and vacuum lines.

Final Check:

Start the engine and observe performance. Look for signs of fuel overflow or rough idle. You may need to re-adjust the idle mixture and speed after float adjustment.