I wouldn't worry too much. The petrol gauge is about as useful as a chocolate teapot or that ashtray I fitted on the front end last year.
That was your big mistake Celtic, never, ever, ever mount an ashtray at the front of a motorcycle, firstly the ash can get in your eyes and the embers could worse case scenario could set fire to the fuel tank. Mounting it behind the rider is by far the safest bet, but I hasten to add not the most convient.
Anyway my ciggy lighter will never stay alight above 15 mph.
Actually I don't smoke, unlike my little Honda C90 that needs a rebore.