Harley Davidson 7 Inch Air Cleaner
Harley Davidson first version of the 7 inch round Air Cleaner came out in 1941 with the FL 74 ci. models. the first type like the bottom example was smooth (Without center screw) and was based on the old J slots method but without a spring but by a sprung force created by the filter element which got a V shape steel bar built into it. this structure continue until 1954, in 1955 until 1965 the backplate got additional raised bridge which hold a nut to close the cover with center screw like seen on the top example note the lock washer split into two halves...