Yeah, I have that thing. Here's the problem謔* use a funnel. It blocks the view into the tank. I pour gasoline slowly and stop often to see if gasoline is visible in the bottom of the funnel indicating that I should quit filling. But every time I fill it I have gasoline stacked up in the funnel neck indicating that the Honda tank is overfilled.
I have two Honda snow throwers and a Honda-engined power washer. I use the same funnel and gasoline can for each one. The lawn mower is the only one where I have a consistent overflow problem. A sight window (like my old John Deere silver deck) would solve the problem for $1.50. Then I could see the fuel level in the tank.