Psychokitty

My husband owns a 1988 Yamaha Radian, we are having a problem with it starting from the button. It will start occasionally that way, but then most of the time he has to push start it to get it going. Does anybody have any ideas as to what could be causing this? Just trying to narrow it down to hopefully cut down the cost of repairs. Since eventually this bike will be mine I would really like to fix this...lol