If the H-D system is anything like those on four wheeled vehicles, the miles to empty or range or whatever you want to call that function won't reset properly if you fill the tank with the key on. So if you get the r=LO message with a half tank of gas still remaining, try filling it with the key off (not in run, not in accessory). If it still doesn't work right, see your friendly (?) H-D dealer. It will probably be considered normal, or they will scratch their heads and wonder what the heck that r=LO means, or they will syphon all but 1/4 gallon out of the tank so the readout will now be correct. Whatever the outcome, it will give you time to wander around the dealership and spend money on Motor Clothes or Chinese chrome, thus helping the dealer and the economy. ( I think Harley purposely uses substandard parts so we have to visit the dealer's on a regular basis. Keeps them and the dealer happy when we hang around and spend more money.)
Jerry