The o-rings on the tee-fittings need to be replaced, as mentioned above. They might indeed re-swell up and stop the leak in time, but if they have cracks in them (likely), the short-term fix will not be sufficient long term.
Here is a thread on the subject from a forum search...
http://forums.sohc4.net/index.php?topic=92641.0I can't remember from where I got mine, but new o-rings will fix you right up.
These are the supply lines that join the carburetors, ensuring that each carburetor float bowl gets supplied from the main tank, regardless of how many lines feed fuel from the tank. The actual float needles and seats are physically below these lines, so the float bowl overflow tubes are not involved with this leak in any way. This problem will leak any time the fuel valve at the main tank is on.
The first post indicated that the fuel leak stopped once the petcock at the tank was shut--this is the main clue.
Here is one of many online videos on the subject, but you need to watch fast on this one:
https://www.youtube.com/watch?v=sF-zsy6wW9gAll the best,
Shane