Harley-Davidson FL

Harley-Davidson FL is a model designation used for Harley-Davidson motorcycles since 1941, when F referred to the new large capacity 74 cui (1200cc) variant of the V-2 Overhead valve engine (″Knucklehead″) that was introduced in 1936 as Model E with 61 cui (1000cc). The presence of an additional letter L indicated higher compression, offering more power but requiring higher octane leaded gasoline. In the early 1950s, the low compression version was discontinued, and in 1952 also the low capacity EL, making FL the basic model designation of Big Twin engines for decades to come.