Carburettor Breather?

[Dead Eye]

So I've finally be working to try and get my 600 back to life. Got the new carbs in place (thanks noggy) and all the other bits and pieces attached so got some fuel and tried to prime the system of which the fuel pump seems to constantly go mad (obviously the system was entirely empty so initially this made sense)

Ended up trying to fire up the bike, but fuel started coming out of the below pipe (when the bike is cranking)

[smg id=2622 type=preview caption="20150712 130907"]

I though this was just a breather?

... I have just had a thought - could this be the float bowls overfilling?