I usually strap on a one gallon gas container and "test my range" on all my new bike purchases. Top off the tank and set a trip meter. Once you get about 15 miles into reserve ride around within a relative short distance to a fueling location. As soon as the bike sputters get off the road and shut it down. Make sure that you have exactly one gallon and put it in the tank. Then ride conservatively to the nearby station and top it off. You can then determine a good estimate for both range and how much usable fuel the tank will actually hold.