At the mileage you're describing, you should have an outright noticeable fuel leak. If you leave the gas tap on and the bike on its sidestand, do you get a puddle on the floor?
Normal mileage is 40-55mpg (US). In my experience, if you run these bikes non-stop at 90-100mph, they'll still return about 33mpg (roughly 100 miles before you hit reserve).
Last edited by petermholmes; 11-21-2012 at 10:28 PM.