I know that this is pretty basic but it wasn't totally common sense until I applied the principles and thought I should share it with the noobs.
My first complaint (coming from the cager world) is that my bike doesn't have a fuel guage, then my second complaint is that after the fuel indicator comes on, how soon do I have before I am stranded.
So for several months I've been basically topping off my tank based on rough estimates, # of hours I've been riding and general guessing by listening to the swish of gas (if any) in the tank.
Sooo.... the following light came on one day.... use the trip indicator to see how far you go; forget about memorizing your odometer reading as I tried this several times forgetting immediately the reading at the next stop light.
so here is the common sense method...
1. fill up your tank till its brimming
2. reset your trip odometer to 0
3. ride until you the "need gas" indicator comes on or whenever you think you need gas.
4. note the reading on your trip odometer
5. start again at step 1.
look at the trip reading in step 4 (this is how far you can go until the light comes on). The receipt in step 1 will indicate the amount of gas consumed for the distance traveled in step 4. You won't know the distance travel the first time you fill up your tank.
so divide the two... Km traveled / # of litres = km/litre
With my high rpm riding style I'm getting about 11km/per litre and about 160km before my indicator light comes on. My tank has a capacity of 18 L and a reserve of 3.2 L so theorectically I can travel another 33.3 km before I am stranded.
Leaving my bike on the trip odometer allows me to know how much fuel I have left since the light will come on at around 160+ ...
I know this is all basic.... but I figure that since I had to figure it out, someone else out there might be in the same boat...