Why doesent my motorbike fuel guage work? Help?

you answered your own question, when you manually lift the sender arm it reads on the guages so the problem is with the send float, take it off and see if its punctured other wise figure out why it is sinking most now days are a plastic material that floats youll just have to look at it and see, but the guage and the sending unit are allright its the float, somehow,