What does a knucklehead engine look like
The bike they took to Daytona had a 61ci EL motor, twin carbs, high lift cams, and high compression pistons. The gearing in the Knucklehead was good for a theoretical mph. To help cheat the wind , sheet metal covers enclosed the forks. One half of a gas tank was fashioned into a small fly-screen and huge innovative for the time streamliner bodywork covered the entire back end. Interestingly, almost every photo of the machine shows this bodywork in place, along with an enclosed front wheel.
That, however, is not how it looked when Joe Petrali thundered across the Daytona sand. Back with the pit crew, Joe ordered the bike stripped of everything but the fork covers and fly-screen. Learn all about the H-D Twin Cam engines right here. The result was a top speed of Ever heard of the Booze Fighters?
His good friend and fellow club member, C. When reassembled, the engine looked like a stock Knuckle, but what they had was the first Harley- Davidson Stroker and the ultimate street sleeper. Clausen, together with Bud Hood, went on to expand on the idea with a full-on drag engine. With high compression pistons, hot cams, and twin Riley carbs, though, the standard cylinders blew apart. Undeterred, Clausen made his own from blocks of solid steel, finishing the fins by hand. The highly volatile fuel was hand-blended on the day to allow for temperature and humidity changes.
The fire-breathing Knucklehead only had to take a practice run, and the flyboys threw in the towel. Pilot Irvine Prait, saw the bike run, knew his jet could cover the quarter mile in around Although the Rolls-Royce Merlin engine was propeller-driven, it was faster down the runway than the jet. The race was extended to a half-mile, and the fighter was allowed to start first. The overhead-valve Knuckle roared down the runway thundering past the plane.
It crossed the finish line four plane lengths ahead! Although off to a shaky start when first launched, the Knucklehead remained in production until Harley-Davidson had already moved away from the hybrid F-head to the Flathead side-valve and so Harley-Davidsons were acquiring a reputation for reliability and deservedly so.
But management at Harley-Davidson wanted to get to market with a viable overhead valve engine motorcycle and William Harley created a design and got engineers Hank Syvertson and Joe Petrali to hammer out the details to create a commercially viable overhead valve V-twin engine. V-twin engine with a 6. The new bike looked impressive and was impressive to ride.
The frame was a cradle type with twin down tubes and stronger front forks than the previous models. The specific problem was oil leakage from the cylinder head covers, rather a lot of it. So they had attempted to use separate rocker boxes bolted to the head. The shape of the rocker boxes was complex and so with the usual expansion and contraction of the cylinder heads under daily use conditions the gaskets were simply unable to keep the integrity of the seal for extended periods of time summer and winter in all the various conditions a motorcycle is typically used in.
In addition to the oil leak problems the metallurgy of the exhaust springs was not sorted out in the early production bikes. This resulted in valve spring breakage.
The year brought stiffer valve springs and a smoother clutch, along with splined pinion and oil-pump drive gears for added strength. Placing neutral in between 2nd and 3rd gear was an unpopular design that lasted only one year.
All year Knuckleheads were hand-shifted. From through , all Knuckleheads displaced 61 cubic-inches. With consumers requesting more power, a 74 cubic-inch version the FL was offered in This was derived from a 3. Both size engines were offered from to From to , the taillight used was the "beehive" style. No frame number was used. The knucklehead was a Harley-Davidson motorcycle engine, so named because of the distinct shape of the rocker boxes.
The engine is a two cylinder, 45 degree, pushrod actuated overhead valve V-twin engine with two valves per cylinder. The engine was manufactured until and was replaced by the Panhead engine in The Knucklehead-engined models were originally referred to as "OHVs" by enthusiasts of the time; the nickname "Knucklehead" arose from the California chopper culture of the late s.
As the design of Harley-Davidson engines has evolved through the years, the distinctive shape of the valve covers has allowed Harley enthusiasts to classify an engine simply by looking at the shape of the cover. A knucklehead engine has round knobs on the cover resembling knuckles that give the knucklehead its name. We're doing our best to make sure our content is useful, accurate and safe.
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