oil light on speedfight 2 100

how come it never seems to work or warn me when my oil is low, i had no oil few months back as my bike would not start at all and the warning light was not on. is there a commen fix for it

 

maybe the bulb has gone

 

mabye although when i start the bike ele start the oil lights goes on for a sec then goes of when the bike starts

 

get the diagnostics sorted on it??? or go to your local m.o.t center see if they can fix?