If you are new to the bike, make sure the proper bulbs are in their sockets. I think 1157's in the back and 1093's up front, but double check me on that. Also, if one bulb on a side is blown it'll occasionally make the light come on and stay on rather than flash. Also, my '78 wouldn't flash until the engine speed was up, changing to a $7 flasher from Auto zone solved that.
Chris in Boston