FL is a model name for motorcycles produced between 1941-48. The 74 cu Knucklehead engine and the type of suspension - Springer forks or large-diameter telescopic front forks - were the major components of these large frame motorcycles.
1 pt = 16 fl oz 16 pt = 256 fl oz. Without taking the time to work it out, it looks to me as if that's probably greater than 74 fl oz.