One nipple (left) is the overflow in the event the tank is overfilled fueling or water gets around the filler neck under the cap. It drains out a direct hose to the left, behind the starter motor and beside the gearbox to drain to the tarmac behind the engine (usually "zip-tied" to the braided oil return line to the back of the sump.
On US spec V11, the other nipple (right) has a rubber seal from the cap to the tank (is it there?) and plumbs below the tank through a one-way valve (that can become less than vertical and fail, yielding "tank-suck" vent failure) to a pair of charcoal canisters that were placed in the tool tray under the seat which were then plumbed, separately, to vacuum taps from both intakes (are those plugged, capped, tubed together, or left open?), and two separate "drains" or "vents" to a cadmium plated bracket at the back of the gearbox bottom.
Other than the vacuum lines, all of my hoses were US made 1/2" double walled fuel line . Twenty feet of it! (I kid you not. I measured it. ) The whole mess weighs five pounds. (No, seriously, I weighed it. )
I am seriously not putting it back on. Unless maybe Walter Peck shows up from the e-pee-a