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Engines and parts for Harley-Davidson

We offer complete engines for custom projects and spare parts for the air-cooled V engines from Harley-Davidson: for the F and J models, for the sidevalve D, G, U, V, W, and for the OHV models with Knucklehead, Panhead, Shovelhead, Evolution and Twin Cam engines, often from brands like S&S and Cannonball. And, of course, many things for those looking for more horsepower, displacement and performance: camshafts from Andrews and S&S, cylinder heads and Sidewinder kits, strokers, high compression pistons from Keith Black ...

Harley-Davidson is known for its V-twins. The two-cylinder 45° V-engine is an icon and characterizes the appearance of Harley-Davidson motorcycles to this day, so much so that it has been imitated again and again, e.g. in the soft chopper wave of the 1980s and 1990s. However, the Harley-Davidson guys were not the first to use this engine design.

Do all Harley-Davidson motorcycles have a V-engine?

Actually no. The first bikes to roll out of the legendary shed in Milwaukee were single cylinders. The first V engine was built on a trial basis in 1907, the V-twins were on sale in 1909 - still with an automatic or "atmospheric" intake valve - and then from 1911 onwards - with a mechanically activated intake valve. (The automatic intake valve was a real performance brake.) The single cylinders were offered parallel to Twins until 1918.

From 1919 to 1923, the factory presented longitudinally mounted boxers to the public. However, this remained an experiment, just like the BMW copies with transverse engine and cardan drive from the time of the Second World War. The single cylinders returned to the sales program in 1926, with a side-valve engine - and for the first time as standard - an OHV engine, and remained until 1934. Two-strokes were also offered in the 1950s and 60s. Models with water-cooled V-engines and 60° cylinder angles have been produced since 2002 and electric motors since 2020. Nevertheless, the name Harley-Davidson still stands first and foremost for air-cooled V-shaped engines with a narrow 45° angle.

Which Harley engines are available? Do the Harley-Davidson V Twins all work the same?

Second question first: let's leave out the Revolution generation and say "in principle they do". Yes, the materials have changed and improved. Aluminum has replaced cast iron, there are O-rings and shaft seals made of plastics where felt, leather and bronze used to be the material of choice, seals are now made of composite materials, bearing materials have been further developed. Nevertheless: the engines have crankshafts with heavy flywheels, two cylinders are positioned exactly one behind the other at a 45° angle, the connecting rods run as an interlocking pair ("knife and fork") on a common crankpin, the camshafts rotate not far from the right crankpin in the basement and the valves are actuated via tappets and - with valves in the cylinder head - pushrods.

The very first generation of Harley-Davidson engines

had an exhaust valve standing on the side of the cylinder and an intake valve hanging (coaxially) just above it, both valves were housed in a pocket cast onto the cylinder. Incidentally, "upright" and "suspended" here refer to the direction in which the valve head points; the plate is effectively the head. As the inlet valve is located above the exhaust valve, the English term is inlet over exhaust, or ioe for short. In American parlance, this valve timing system is also known as a "pocket valve" because the two valves are housed in the aforementioned pocket.

Side valve V-Twins, called Flathead

In 1929, the period of side valve V-Twins began at Harley-Davidson (extensively tested before on Sport and single-cylinder engines). On the right-hand side of the cylinder, the intake and exhaust valves were arranged in a neat row one behind the other, the valve heads were located next to the cylinder bore, the cylinder head was actually just a cover and contained no mechanical parts. In English, this arrangement is called side valves or sv for short. Why side valves? One of the main reasons seems to have been the material of the valves. In IOE engines, the intake valve was often torn off and the valve disk fell onto the exhaust valve or the piston, causing damage. Of course, valve heads can also break off on side-valve engines, but they remain in place and do not cause any additional damage. Legend has it that you can even continue driving if you shut down the affected cylinder and unscrew the spark plug. V-shaped side-valve engines were available with 45, 74 and 80 cubic inches of displacement, i.e. 750, 1200 and 1300 cc.

With the 1936 model year

the V engine was fitted with valves suspended in the cylinder head. The intake and exhaust valves were actuated by a single camshaft via tappets, pushrods and rocker arms. This principle of valve train has remained the same to this day. As the valves are virtually positioned above the cylinder head, they are referred to as over head valves, or ohv in short. Nowadays, overhead valves are the only form used on V Twins. The compact combustion chamber shape offers considerable performance advantages over side-valve and IOE models.

The first of these engines still had exposed rocker arms. It was not until 1938 that the respective rocker arm was placed in a common sheet metal housing with its valve springs. Customer friendliness has always been a top priority for Harley-Davidson and customers did not particularly like oil-stained pants. (If you look at the engines of other brands, unencapsulated valve trains were quite normal until the 1940s). The further developments of the OHV engines were externally recognizable by the changing covers of the valve train on the cylinder head. The bikers invented nicknames for this: Knucklehead, Panhead, Shovelhead. For almost 50 years, the factory itself only referred to OHV engines and only gave them their own name for the Evolution models. Their successor series are called Twin Cam and Milwaukee Eight.

Haven't we forgotten something?

Yes, that's right. Parallel to the development of the valve train and the cylinder heads, Harley also took care of the housings. To this day, the engines of the big Twins are actually independent assemblies. Although the housings for the primary drive and the manual transmission are bolted on, they are actually three separate parts. Not in the Sportster series, however. In 1952, the small Twins with the 45 cubic inch engine were replaced by the K models. Like the 45cc models, these had side valves and 750 cc displacement, but a common housing consisting of two halves for all three components: Engine, manual transmission, primary drive. Unit construction in English, block engine in German. In 1957, the block engine was fitted with OHV cylinder heads, while the four camshafts of the side valves remained - after all, continuity was important. In any case, that was the birth of the Sportster. (Another word coined by the Factory. It was written in bold letters on the cast aluminum primary covers from 1957). With minor changes (Evolution cylinder heads, five-speed gearbox), the good old Sportster series continued until 2020. Since 2021, the Sportster has had an S in its name and a completely different engine based on the Revolution Max: with 60° V, four valves per cylinder, double overhead camshaft and water cooling.

Have any questions?

Our service team will be glad to help out: Mondays - Thursdays 08:00-17:00 CET, Fridays 08:00-16:00 CET, Phone: +49 / 931 250 61 16, eMail: service@wwag.com