I have had a few sponsors for several years and know the game pretty well. In fact, if you Google it, my website comes up with a well-read page I wrote a couple years ago explaining it all in detail. The companies I have worked with are mainly interested in a couple thing: exposure and sales. If they give you gear (investment) then they expect to at least double their return in sales. If your trip is in popular mainstream magazines or turned into a Discovery Channel show they will come begging. Very few bike tours get this far. For most of us, exposure and sales potential are directly related to website traffic. If you have a busy website, they know they can profit. Otherwise they make their money by selling things to bike tourists - not giving things away.
Most cycle tourists think if they are on a epic trip in far flung places, sponsors will be attracted. In my experience, they do not care where you go or even if you ride it all. They just want the eyeballs and sales from website traffic. What you have on your jersey or logos on your bike are not very profitable unless you are on a big TV show.
I recommend building web traffic first, then asking for sponsors. I could write a lot more but this gets to the heart of the bike touring money game.