The amount of fuel carried makes little difference. If you always know you fill up to the bottom of the filler tube, and always fill up when the light comes on, you will know your range unless you are looking to risk it and take the tank to fully empty.
For the 1999 bike, the capacity, listed by Yamaha, is 18 litres. This is from empty to the bottom of the filler spout. For the later bikes, it is 21 litres. Both of these numbers have a theoretical 3 litres left when the fuel light comes on.
