Need to determine where the gas "under the carbs" is coming from. Is it the overflow tube(s) on the carbs? The fuel line feeding the fuel rail for the carbs? From the petcock, dripping outside the fuel line? Is it gas?
If it's coming from the overflow tubes, chances are the floats are not closing all the way. This could be as simple as tapping on the side of the carbs with a hammer handle to free them up. It might also be due to a bit of crud between the needle and seat for the float. You'll need to pull the carbs, and the carb bowls to verify that.
If it's coming from the fuel rail, you'll probably need to pull the carb bank and take apart the fuel rails. There are some O-rings to seal up the pieces. Check them all, and replace the suspect ones.
If it's coming from the petcock or the fuel line, tighten and/or replace as needed. It might not hurt to run an in-line fuel filter, to keep dirt out of the carbs. Cheap insurance. Look for either a paper or brass element, with 1/4" inlet and outlet tubes. I got mine at NAPA for about $6.
I hope this helps.
Luke M
Used to have a 1979 CB750L, sold it as a parts bike, now riding a slightly modified 1984 VT700C. Network/Field Engineer. Central OH, USA, Earth, Sol System, Milky Way Galaxy, Universe.