What may be the coolest looking motorcycle engine of all time, the Panhead was originally manufactured by Harley-Davidson from 1948 through 1965, but 25 years after production ended, popularity and demand was so strong that several aftermarket companies began reproducing them.

Although the Knucklehead was one of the Motor Company's crowning achievements, by the mid 1940's the Big-Twin was in need of an update. Harley engineers updated the Knuck's upper-end with aluminum heads which reduced operating temperatures, and added hydraulic valve lifters which reduced engine noise. The new heads were topped off by redesigned rocker covers which resembled upside-down roasting pans, prompting the nickname "Panhead."

The V-twin engine displaced 73.73 cubic-inches (advertised as 74ci), which was derived from a 3.44" x 4" bore and stroke. With 7:1 compression ratio, 50 horsepower was produced at 4,800 rpm. The bottom end was basically unchanged, but the engine cases were modified for the new cylinders, and a new camshaft was designed for the new valve system.

A new frame had double down-tubes and was stretched to accommodate the new taller engine. It became known as the "wishbone" frame, and came with a mounting plate for engine-guards as well as a steering lock. Wheelbase was 59.5 inches.

The Panhead came with a fuel capacity of 3.75 gallons, a one-gallon oil capacity, and had a top speed of 100 miles per hour. Total weight was 565 pounds. Transmission was a separate 4-speed unit. Like the Knucklehead, the Panhead was offered as either the EL (61 cubic-inches) or FL (74 cubic-inches).

Color options included Flight Red, Azule Blue, and Black. The first year of the Harley Panhead was also the last year of the springer (leading-link) front end.

In 1949, hydraulic front forks appeared on the new 'Hydra-Glide' models. The modern telescopic units nearly doubled the amount of wheel travel, and many thought it gave the bike a cleaner, more modern look. Along with the hydraulic forks, the front brake drum diameter was increased to eight-inches.

The hand-clutch/foot-shift option became available in 1952. It took a few years to catch on, and many Panheads still had the foot-clutch/hand-shift setup well into the sixties. (Hand-shift models were offered by Harley-Davidson through 1978.)

A clutch booster, nicknamed the "mousetrap", was added to the Panhead to aid in hand-clutching. It was attached to the front left down-tube with a spring hidden by a vertical cover. These were known to be troublesome, and 'mousetrap eliminators' have been around for nearly as long as the mousetraps.

Designed to reduce the likelihood of burnt exhaust valves, a rotating cap was placed between the valve stem and rocker. In 1953, the lifters were moved from the top of the pushrods to the bottom of the pushrods. Internal modifications were made to the muffler, along with a name change from "Mellow-Tone" to "Low-Tone".

After nearly 50 years as Harley's arch-rival, the Indian Motorcycle Company went bankrupt in 1953. When Indian closed its doors, Harley-Davidson, now the only American motorcycle manufacturer, saw increased sales.

50th Anniversary Harley-Davidson

Why 1954 and not 1953 is a topic of debate - all subsequent H-D anniversary models would use 1903 as year one. 50th anniversary models were specially trimmed and decorated.

In 1955, the Panhead's intake manifold, carried over from the Knucklehead, was upgraded with O-ring style ports. The solid lifter/hydraulic pushrod was switched to a solid pushrod and a hydraulic lifter/tappet. Also this year, valve covers went from 12-bolt to 6-bolt. This lasted for less than a year, and by late 1955 the 12-bolt cover was back to stay.

The year 1958 was very significant in Harley Panhead history. First was the introduction of rear suspension, making the Hydra-Glide the Duo-Glide. Second was the addition of hydraulic rear brakes (all earlier models had mechanical rear brakes). Other improvements for 1958 were a new oil tank, as well as transmission and clutch upgrades. Over the next several years minor improvements were made, and in 1965 the last major step was taken.

1965 Electra Glide

In the Panhead's last year, buyers were given the option of electric starting. The Big-Twin now housed a 12-volt ignition system and an electric starter. The left engine case was changed to accommodate the electric-start. This left case and primary cover were used up through the 1969 Shovelhead.

Also for 1965, the Harley Panhead engine came with an automatic-advance distributor, which can be retro-fitted to any earlier (1936 to 1969) 61" or 74" OHV Big-Twin. An optional 'King of the Highway' package included a chrome battery cover, chrome oil tank, directional signals, white saddlebags, and more.

The Duo-Glide became the Electra Glide, a name that endures to this day. Initially, not all riders liked the electric start, as it added 50+ pounds of weight, making the bike about 10 mph slower at the top end. A hyphen is used between Hydra-Glide and Duo-Glide, but not Electra Glide.

Harley-Davidson motorcycles had two diameters of seat posts from 1929-1999. Most Knuckleheads, Panheads, and Shovelheads (up to 1981) have a seat post diameter of 1.18" diameter (bushing ID 1.185") On 45" solo bikes and Servi-cars from 1930 to 1973, the seat post diameter is 1.06" (bushing ID 1.065"). There are slight variations in the seat bracket but for the most part they will interchange.

All Panheads have the VIN located on left engine case. No frame number was used. The first two numbers are the year and letters (up to four) are the model designation. The last numbers are the production number.

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