Scare up a wiring diagram from an online forum such as Hondatwins.net and learn what the key does - ie 'black-connects-to-yellow' and 'red-connects-to-blue-with-white-stripe' or whatever.
Then, find the electrical connectors nearest the ignition switch (in the headlight shell?) and jumper those connections.
There, you've simulated turning the key on. Done.
Kirk