Rigid frames make absolutely stunning motorcycles - clean,
low, mean, lean look - but they are a challenge, not only to maneuver, but it can be a little hard on an already weary rider
after a long ride, or a long day of bar hopping here and there. Nowadays, great after-market products can be applied
for different purposes, making the ride a bit smoother while maintaining a clean, low look. Harley custom builders will
always find a way, just as the Harley-Davidson motorcycle has evolved over the years, so have they. Inevitably, these
modifications led to the idea of an internal, hidden swingarm which would enable builders to manufacture a rigid-looking frame with the advantages of a swingarm without the bulk. We come to the logical introduction of the much awaited Softail. Since its introduction, the Softail frame is by far the most commonly used frames for building custom bike, or stripping a stock model of all unnecessary items.
Harley-Davidson manufactured the FL model 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, especially on Harley-Davidson Softail Frames with traditional styling, 16" front wheels, and either Springer forks or large diameter telescopic front forks.
It used a 74 cubic inch (1,210 cc) version of the Knucklehead OHV engine that powered the EL in 61 cubic inch (1,000 cc) form. The FL shares its frame with the EL and with the U
and UL, which used a 74 cubic inch flathead engine. The FL replaced the UH and ULH, which used th same frame with the
80 cubic inch (1,340 cc) Flathead engines.
The FL continued relatively unchanged until 1948, when in
and the EL were given redesigned Panhead engines of the same capacities as before. The Harley-Davidson Panhead Engine had several improvements over the earlier Knucklehead, including aluminum cylinder heads to reduce weight and improve cooling, also adding self-adjusting hydraulic lifters.
The U and UL Flathead V-Twins were discontinued in 1948, leaving the OHV EL and FL models as Harley-Davidson's large-frame motorcycles. In 1949, a year
after receiving the Panhead engine, the FL was given a new front suspension and a model name to go along with it. In honor of their first production
motorcycle with hydraulically-damped telescopic forks, the FL was officially calle the HydraGlide. This name would change
twice in the history of the basic large framed FL bikes, each time signalling an improvement in the bike's technology.
In addition, the Glide ending would be used on other models, based on both the FL and FX formats.
In 1952, the HydraGlide transmission format was reversed
from hand shift/foot clutch to foot shift/hand clutch, although the original format continued to be offered as an option until
1978. 1952 was also the last year of the 61 cubic inch (1,000 cc) EL, making the FL the last remaining large frame model.
A more highly tuned engine with high compression heads, higher-lift cams, and polished ports, was offered with the FLH version
of 1955. The FLH designation has continued to the present.
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