If the tank is leaking you will see an area that is darker that the rest. Honda puts undercoating on everything and the gasoline will discolor it. A messier solution would be to remove the plastic guard that protects the filler hoses and breather lines (driver side in front of the rear wheel) and look for wet spots. If you don't see anything then dust it in baby power and look for the wet spot (don't go there). After all that you can be pretty sure you're not looking at a tank leak. Then look under the hood with the key on and engine off and run the fuel lines from the filter all the way to the return lines.