I have the same problem with my bike a Four gallon tank and I am constantly turning it to reserve at 110 - 140 miles depending on how i am riding. The bike can do 62 MPG at normal 925-45 MPH speeds) and considerably less at high speed cruising. I then find myself with about a 2 gallons in reserve when i hit the gas station. As best i can tell this is not a malfunction but a guestimate on Kawasaki´s part to not have you run out of gas. I now find myself just turning the knob to reserve and filling up at 165 miles. Even then I am sometimes puttin in less than 3 gallons.