Just curious-when I fill by bike up to the silver nozzle holder inside the tank, I can just keep filling it up, let it bubble down, fill it up, let it bubble down and can do this till it makes me uneasy so I stop. Where is that fuel going-I thought it might be going out the vent lines but nothing. Is that the reserve tank? Sorry if this is a dumb questions-none of my other bikes have ever been able to add more than a gallon once its "initially" filled up.
There's not actually a reserve tank. Observe:
So, on older bikes with a manual petcock, setting it to on or primary, would open the valve for the primary fuel pickup. When the engine started to sputter, you'd flip to reserve, which would close the primary and open the reserve. It gives the illusion that there's a separate take, but it's basically just a warning system of just one tank getting low.
I'm 99% sure the Fz8 with it's electronic reserve, is actually just one pickup tube but the tank has a float. When the float reaches a certain point, the dash indicates that you're now on reserve.
To answer the question you asked, the fuel isn't going anywhere. Fuel pumps at filling stations spray the gasoline at a fairly high flow rate/pressure. This splashing into the tank creates bubbles. But unlike soap bubbles, they pop quickly, which then allows you to add more gas.
