Fuel gauge confusion

[Morbius]

Hi all.

My fuel gauge has always confused me. I have a YBR125 which is supposed to have a 13 litre capacity.

The other day I got home and the needle was just above the red section that comes before empty. I took my 5 litre fuel can to a well known supermarket's petrol pumps and filled it. I then went back home and emptied all 5 litres into the bike. The needle then went to full. I was expecting it to need another 8 litres to get to full.

Now, today I took the bike to work, which is 25 miles each way, so 50 in total. When I got home in the evening, the needle was at halfway. Now, if we assume that means half of 5 litres then that equates to roughly 90mpg, which is par for the bike.

Are all fuel gauges this inaccurate? I suspect probably not. If I had to guess, I reckon that something might be up with the fuel sender. Because I'm still fairly new to motorbikes, I'd appreciate any advice or suggestions.

 

[Morbius]

OK, I think I've got to the bottom of it. I took the bike to said supermarket forecourt to fill up and kept going until I could see for certain that the tank was full. I now know that full is a small amount past the full mark, so there must be quite a healthy amount of fuel remaining when the needle gets near to empty. That's no bad thing really.

 

[Morbius]

On the YBR's it says way over full for about 50 miles, then it starts dropping rapidly. Mine ran on empty (so it said) for nearly a week. I got 260 miles out of that tank.

That sounds about right!