Check the manual, my Indian has a lip just inside the tank the manual says just as it comes over that lip your “full”.

US, west coast, we have systems on the nozzle which prevent dispensing gas unless the nozzle is well seated, in order to pull gas fumes back into a return built into the hose. Here's an article.

I usually have to forcibly override it by pulling back on the plastic ring around the nozzle's base, otherwise I'd only get 2/3 of my tank. I stop a bit below the inlet of the tank, gasoline from a cool underground tank will slightly expand in summer heat.

Good idea for the environment, little bit of an annoyance but no big deal.

I put one 500 yen coin into the machine. Sometimes I get change back. :P (I drive a lil super cub).

but yeah like others are saying, just fill it mostly to the top. No worries.

My Honda Metropolitan has a little bar at the bottom of the fuel fill hole. Pretty simple. My older XR500 though is just a big hole at the top...