Sounds like a bad float valve or at least it's not sealing consistently....perhaps it's tilting or you have a bad float? Double check the float height per the above and see if it's consistent with where you set it to make sure it didn't change somehow. Maybe vibrations make it move around irregularly?
One thing that I sometimes do is remove the bowl (with a floats hanging), attach a bit of hose to the fuel inlet and give a gentle blow....you should be able to blow air without issue...now raise the floats gently with a free hand, until it seals the float valve...at some point it should stop your air flow. If it doesn't stop it entirely, the valve is bad. You can also get a general idea on where the float is when it stops air flow to see if it's about where it should be...NO, it's not scientific/precise, but it does help a bit with perspective.