If that is the case, your fuel level is likely at (or over) the brim to the auxiliary venturi passageway. In other words, your float levels are likely too high. Are your air horns wet with fuel after running the engine?
Proper float adjustment is done as follows:
This is assuming you're using the right side of the rod to dip into the fuel, as pictured. Adjust the floats so that the RIGHT side of the sliding collar is flush or slightly to the left (1mm) of the RIGHT hash mark on the PC rod. That should measure 25mm using the depth gauge on a caliper.
Here's how I set my floats:
Write down your current float levels as measured with a caliper depth gauge, using the method as described above. Sounds like you're at 23mm. Remove the cover and put it upside-down on a workbench. Using a caliper, measure the distance between the float and the cover when the float tang just touches the needle valve, as shown in the 8.5 dimension in this photo:
DO NOT worry about the actual number but do write it down. We're only concerned with the difference. If your floats are too high, you need to increase this measurement by the amount that your floats are off, i.e. this is a 1:1 relationship.
For example, if your current float setting is 23mm as measured from the top and we want it to be 25mm, then increase the distance between your float and cover by 2mm. Visualize what this does and you'll understand. That means that if you measured 8.5mm currently, then that needs to be increased to 10.5mm. By setting floats this way, I can usually get them close, if not perfect, in one try.
DO NOT be concerned if all three carbs have slightly different measurements between the float and cover. We're only worried about the actual measurement from the jet stack shelf down to the fuel level (with the engine running).