Whats up with my overflowing carbs?

After riding my 1979 kz650b3 and it has sat for a while when I move it just a few feet,like pushing it from one side of the garage to the other,a considerable amount of fuel comes out of the overflow tubes onto the floor.What's up?It runs great,I don't get it.

pull the float valve assemblies off completely and clean them..

Or try some seafoam.

Is your petcock functioning correctly? If it's leaking gas after parking, and you still have the stock vacuum petcock, your petcock is either set to prime or the vacuum diaphragm isn't working and it's letting fuel by when the bike is shut off. If you determine it's the petcock I'd highly recommend replacement. Jeff at z1enterprises has a nice vacuum unit listed as a suzuki part that bolts up to the 650 with minimal mod (I believe you have to rotate the back plate 90 degrees to fit correctly, nothing major).

If it's not your petcock check and clean the float assemblies and set the float heights with the clear tube method.