[5th_bike]

Hm, first thing coming to mind is the gas hose, between the petcock and the carburator. It should have a clip at each end, to squeeze it tightly around the nipples. If a clip is missing, buy it. If the hose is bad (cracked), buy a new one. ASAP, because leaking gas is very dangerous.

The other 'thick hose' is at the bottom of the bike, it should have a cap and will drop goop (water/oil/gas) that collects in the air filter housing.
Close by is another hose, thinner, which is the carburator overflow.
Hope it's not one of them.

No gas should be flowing when the engine isn't running, except when the petcock is set to "pri" (prime) (lever points down). Make sure the petcock lever is pointing forward in the "run" position. Except when you run oout of gas, then point it to the rear - "res" (reserve).