Knucklehead Ahoy – Motorcycle Find of the Day

Dar Holdsworth is the owner and operator Brass Balls Bobbers and Darwin Motorcycles, and his Navy F3 Rocketeer, based on one of his ‘kit’ machines, is one sweet ride. Built for the Rolling Thunder 25th anniversary in Washington DC, the Brass Ball Bobbers Rocketeer F3 became this US Navy tribute custom, and what a tribute it is to our fighting men.

The Navy F3 Rocketeer is built around a 93″ S&S Knucklehead mill. It features a 6-speed transmission, took something like 300 hours of machining and fabrication, and a custom gas tank and rear fender which were milled from solid aluminum billets.

Add to the list Avon tires, Wilwood front brakes, an Autometer gauge, the Alloy Art Panhead headlight and a custom Kyle Hix seat, and you have one fine ride, my friend.

It’s a throwback look to a time when Harley-Davidson ruled the world, but it’s the Knucklehead motor which makes the bike a complete statement. It was, after all, the Knucklehead which signaled Harley’s switch to the now ubiquitous V-twin configuration (from the previous ‘flathead’ design) and overhead valves which is still the basis for the Harley motors of today. It was the overhead valve design which led to the change in shape of the new rocker covers on the powerplant, and that now precious motor was immediately christened the “Knucklehead” by owners for its distinctive look. The nickname has, with time, achieved iconic status.

The ‘Knucklehead” engine was a two cylinder, 45 degree, pushrod actuated overhead valve V-twin with two valves per cylinder, and it was manufactured until 1947, though replica engines, cases and parts are still manufactured today by various companies like the one on this Holdsworth creation.

A relatively low production run of 1,829 Knuckleheads produced for 1937 means that these lovely pieces of engineering are sure to hold their value for many years to come, and you can have this one for something over $100,000.

The EL Knucklehead motor featured a new recirculating oiling system which eliminated the messiness and inconvenience of the previous ‘total loss’ setup from the flathead days, and the new features on the 1936 EL motor, principally those rocker-shaft covers and air intake, marked a sea change in Harley design.

The timing case cover was designed and re-designed no less than three times during the initial model year of the EL, and each change was considered an improvement by riders. When you consider the original EL’s welded fuel tanks and the tank-mounted instrument panel, you can see the genesis of a styling cue trend still in evidence on Harley models to this day.

It was a stunt which, back in April of 1937, really made the Knucklehead a legend. Fred Ham, a Pasadena motorcycle cop, took his Model E to Muroc Dry Lake where he set up a five-mile circle with flags and flares and then set off on an all-day, all night endurance run. Stopping only for fuel, oil, refreshments (and taking time to repair a broken rear chain during the 20th hour of the marathon), Ham traveled 1,825 miles, averaging 76.02 mph. Ham’s ride set 43 new speed and distance records and his ride created the legend of the Knucklehead.

Check some other work from Darwin Motorcycles here…


Dar Holdsworth’s Foremost Insurance Chopper

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