FL is a model designation used on motorcycles manufactured by Harley-Davidson from 1941 to present. Mostly applied to Harley's large-framed bikes, including the current Touring series, the FL designation is also used witFL is a model designation used on motorcycles manufactured by Harley-Davidson from 1941 to present. Mostly applied to Harley's large-framed bikes, including the current Touring series, the FL designation is also used with their Softail series,h their Softail series,