Fuel Tank overflow drain tube.

[17-CB-002]

There is no gate. The ‘Overflow’ hose is part of the vapor recovery system, if you have it in Maylasia. If you do the hose goes to the evap canister where vapors can be drawn into the engine if the purge valve is energized. There is also a drain hose out of the canister. If fuel is coming out the canister is most likely saturated.

You may not have all this on your bike. In any case it sounds like you are overfilling the tank. There is no way for fuel to reach the overflow tube if properly filled.

Coincidence, I was just studying my seamless gas tank construction last evening...
On my 2017, I have 2 tubes coming out from under the tank.
1. One goes to the EVAP Charcoal Canister (Vapour/fume recovery). (The repair manual calls it "Canister hose or Breather hose"
2. Drain hose (as per HONDA description: .... for draining out gasoline that may leak during servicing) - {From parts fiche #7 Drain Tube #17543 MGC JBO}

For 2013 to 2016 models, from the repair manual, there is only one hose coming out of the tank and calls it ... "breather hose"