Ah, I see. I was unaware you got the BS36's. Wise choice. A leak in the carbs can mean a lot of things actually - sticky float needle, sticky floats, bad bowl gasket, etc. If you can see the leak on the carbs, it's most likely the bowl gasket.
Carb tuning is a dark and mysterious art. Actually, it's just a lot of work. Nobody will be able to tell you for sure what your carbs will need, and you can't really find out until the bike is able to be ridden.