You don't need a fuel gauge. You can use the tripometer/odometer. Most motorcycles don't have fuel guages and hte tanks are terrible small, so you learn to ride unti lyou get to 120-150 miles then refuel.

OS if you know what the typical mileage is for that tiem of year and road conditions, then just only use 10-12 gallons of ht ecqapacity and caculate your range based on that. SO if you get 30mpg on the freeway, you should refill between 300-360 miles without worry of runing out of gas. In city driing when getting 20mpg, you can stop safely after 200-240. Etiher way, your looking at at least 6 hours of fuel.