Don't know about a '74 but my '80 takes 24 oz according to the manual. I believe there should be a bleed valve on the side that overflows when it's full. Someone with the same year will chime in I'm sure.
If there is a bleed hole, put 3/4 of a quart in, prop the bike upright and pull the bleed hole, otherwise prop the bike upright and fill to the bottom of the fill hole threads.