How to Test a Motorcycle Carburetor Float

Test the float on your motorcycle's carburetor if you suspect it is not operating properly.

Motorcycle carburetors use a float-and-needle valve assembly to control the level of the fuel within the carburetor float bowl. The buoyancy of the float pushes up on the needle valve to close off the float bowl fuel inlet when the bowl is full, and prevents overfilling. Fuel height within the bowl is critical to maintaining the proper air-fuel ratio for the engine. Damage to the float can cause an improper fuel height and lead to a poor running condition. Inspect and test the float once the carburetor has been removed from the engine and the float bowl removed.

Things You'll Need

• Phillips-head screwdriver
• Bowl of water

Instructions

1. Inspect the fasteners holding the float bowl pin in place. Loose fasteners can cause the float height to be erratic.

2. Check the float-to-pin connector. Damage to the connector can cause the float height to vary.

3. Check the float pin for straightness. A bent float pin can cause the float to bind and not respond properly to fuel height changes.

4. Remove the float from the carburetor. Check the float for cracks or deformities. Shake the float and listen for sounds of fuel sloshing around inside the float. Any damage to the float is cause for replacement, including fuel inside the float.

5. Immerse the float in clean water and watch for bubbles escaping from the float. Bubbles indicate a leaking float and requires float replacement.

6. Replace any components found to be damaged or deformed.

Tips & Warnings

• Use caution when working on fuel system components. Work in a well-ventilated area away from open flames. Do not smoke while working on the fuel system.

References

• Dyna Evolution Service Manual 2003; Harley-Davidson Motor Company