Greetings from Cairo

My fuel meter has worked relatively well so far but now, all of a sudden the bars are dropping down twice as fast compared to what it used to be. And there's nothing wrong with the fuel consumption.

Has anyone else had this problem and if so, what was the reason?

And one more thing: If I stop the bike at let it stay put for some time, the bars in the fuel meter will rise back to normal, until I start riding again and then they drop down again almost immediately.

Jami