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Harley Knucklehead Bobbers

Before Choppers, there was Bobbers...

This Harley Davidson motorcycle website is all about Harley Knucklehead Bobbers and Choppers. The Motor Company introduced the 61 OHV Knucklehead engine in 1936 in the Harley Davidson EL model motorcycle. This Over Head Valve V twin had a displacement of 61 cubic inches / 1000cc. In 1941 Harley added the FL model bike featuring a 74 cubic inch / 1200cc knuckle head engine.

Knucklehead ?

Photo of 1939 Harley Davidson Knucklehead E61 OHV V Twin Engine. The 61 OHV engine was nicknamed "knuckle head" for the shape of the rocker boxes on top of the cylinder heads. With the protruding rocker shaft bolts these rocker boxes resemble the knuckles of a clenched fist.

The over head valve Knucklehead engines, with their superior inlet and exhaust port aerodynamics and therefore more efficient flow of gasses in and out of the engine's hemispheric combustion chambers, were more powerful than the side valve Flathead engines with their heavier breathing inverted-L shaped combustion chambers. Where the Flathead engines produced about 30 to 35 horsepower, the Knucklehead 61 cubic inch OHV engine generated approximately 40hp while the 74 OHV produced roughly 45hp.

Click this photo to check out this 1939 Model EL Harley Davidson Knucklehead Classic Motorcycle in Original Paint by Norm.

Besides being more efficient and powerful than the Flathead engine, the 1936 Knucklehead engine introduced more improvements, like for example the recirculating oil lubrication system which a year later was also featured on the Flathead engines. (Pre 1937 Flathead engines with their one-way oiling system simply dropped all used oil on the tarmac. If not on your garage floor...)

With its overhead valves protected from dirt under a closed rocker box, the Knucklehead engine in fact was the mother of all later Harley engine designs, via the Panhead, the Ironhead and Shovelhead, all the way up to the Evolution engines and today's Twin Cam engines.

Harley Bobber or Harley Chopper...

A Bobber can de defined as a motorbike of which components which do not contribute to speed have been removed. A matter of weight shedding within the limits of the law... In short: Remove ballast like fenders, side bags, buddy seat, turn signals, etc., and you've got a Bobber. Chop the frame and you've got a Chopper.

Having said that, fact is that many of the original thirties and forties Knuckleheads - just like the Flatheads of the same era - are already of quite spartan design. And old school like Granny's apple pie.

So please do not be disturbed if this Bobber website also shows you a couple of Harley Knucks with the front fender still on!


HD Knucklehead Oldschool / Chopper / Bobber Gallery

Stock Harley Knucklehead Motorcycles

While this website is about Bobbers, Choppers and other modified bikes, we won't hesitate to show you the originals as well. Out of respect. And because we love them!

Look at these beauties: