Gas leaking from overflow tubes

[pekingduck]

After sitting 3 years, I suspect the gas has turned to varnish and gummed up the jets and their passages, and buildup is preventing the float needles from sealing. So the carbs will likely have to be removed and thoroughly cleaned.

If you're in there, I would recommend replacing the metal float needles, if they came with them, with rubber-tipped ones used on all later bikes.