Hi all my fuel warning lights do not work its a 1987 k 100 i cant see both bulbs failed is there a comon fault area to look at first note i have just purchased the bike

Biggeoff,

From time to time a bulb will fail.
Your bike is 23 years old and you don't know when the bulbs burned. One may have burned 10 years ago and the other 5 years ago. The original owner may have ignored the trouble because he didn't rely on them.
Since you just bought this bike, you should replace the 2 bulbs and monitor if they quickly fail.

my bulb is working but i dont know how to read it...within 4L /7L sometime both will light together...