The peculiar sound of a Harley-Davison's engine is, for many, heavenly music. So much that some people resemble that of a brotherhood during Holy Week: pom, pom, poropopom, pom, pom ... Others compare it to the 'pop pop' that is heard when we make popcorn ... And for romantics, it sounds like the Same human heart beat.

Be that as it may, it is evident that it is a unique, almost hypnotizing sound, that some of us put on the spiky hair, and that even the legendary Milwaukee firm has tried to register as a patent, without much success indeed.

What makes a Harley-Davidson sound so different from other motorcycles is nothing but the design of its engine. Like any normal engine, the Harley engine also has two pistons. The difference is that the crankshaft has only one elbow in which both pistons meet. This, combined with the “V” position of the 45º cylinders, produce intervals that give rise to that characteristic sound.

Today we propose to go beyond that unique melody and learn a little more about the history of the Harley-Davidson V-Twin and the engines that precede it.

Harley-Davidson's initial engines offered very little power, unable even to climb a simple slope. In fact, the first motorcycle of the brand had 175 cc, a power of 1.5 hp and a cylinder of 54 mm. Both that first Harley-Davidson prototype and the next two were tested on a bicycle chassis. They were designed to participate in races, but ended up functioning as rotor propellers for boats.

It was in the spring of 1903 when in that Milwaukee shed Harley and Davidson managed to manufacture an improved engine, to place it in a stronger and larger chassis, that of model number 1. It was an open secret that this engine was based on the one designed in France by Dion and Bouton in 1894. The displacement now reached 400 cc, with a cylinder of 74 mm and a power of 3 hp, a power capable, now yes, of ascending slopes. This motorcycle had a total of 5 owners and managed to travel the negligible figure of 163,000 km without major damage.

The company begins to market its motorcycles and it is in 1906 when the firm changes black to a new tone: gray. It is the birth of the slender Silent Gray Fellow, with a power of 4.3 hp in a 500 cc engine.

In 1909, Harley-Davidson presented its V-Twin engine, with a very particular sound and vibration response, installed on the 5D model. The 6.5 hp of power were given by its displacement of 810 cc. A new cylinder was added to the only one of the previous model, with the idea of ​​improving the speed of rotation, even at low revolutions. Thus, with two cylinders operating alternately, the torque remained constant, considerably reducing vibrations.

The two cranks, which went to a single reinforced crankshaft, in turn attached to the flywheel, were its main feature. It also drew attention to the fact that their rockers and rods were left in the air, totally visible to everyone. However, it was not a simple engine to start, because of its compression ratio, and the transmission belt did not work well, so that the motorcycle was withdrawn from the market, while they continued selling their machines with the previous single-cylinder engine.

Although most believe that the Harley-Davidson invented the two-cylinder engine, it is not entirely true. It was not a novel engine for the world of motorcycling, since in Europe, the Grifon, already used it long before on their motorcycles, like its biggest competitor, the Indian, so it was a trend at the time.

It would soon appear a new engine, the F-Head (F in the head). In 1911, the inconvenience of the rear belt is solved with a roller system and now also changes the arrangement of the valves, the intake in the cylinder head, and the exhaust gas, just next to the head.

This is how Harley-Davidson definitely enters the world of racing, even winning some as important as the Tourist Trophy on the Isle of Man, with the Stock Racer 6E. With the victories, the American firm gains notoriety, but also great technical improvements. The 7D and 8E models are born, the latter with a 988 cc F-Head engine; the 10, with kickstarter towards the front, and the J, with 1000 cc.

The W Sport Twin (1919-1923) was the engine that Harley-Davison manufactured for its racing bikes: WF model, with magnetic ignition, and WJ model, with electric system. Its main feature was that the cylinders were arranged in the direction of travel. It had 600 cc of power and also had a primary transmission system by helical sprocket.

Another of the distinctive characteristics of the Harleys, the tear shape of the fuel tank, also arises at this time, specifically in 1920. And at the end of the decade the engine there is a considerable evolution of the F-Head engine, until 1200cc

However, also in 29 curiously, another different engine appears again: the Flathead (flat head), which mount their new V74 models. This third generation engine no longer shows its moving parts. Seesaws and rods change places to be placed on the sides of the cylinders instead of on the head, which is now transformed into a combustion chamber. There were different versions of this engine, as well as several displacements: VL, VM, VLM, D. The latter stood out for having a vertical generator placed in front of the engine, right next to the cylinders, hence this type of Harleys popularly known as "the three cylinders".

During World War II, following the appearance of the BMW and its advanced two-cylinder boxer engines, Harley replied by imitating the German R12 with the XA boxer engines (1942-1943), to ride the motorcycles of the US Army, which They subsequently had their civil version. Harley-Davidson stopped using the Flathead engine for its two-wheeled bikes, keeping it exclusively for sidecar bikes until 1973.

The OHV Knucklehead (Knuckle Head), contemporary to the Flathead, is another of the mythical engines of the Milwaukee firm. It is named this way because the rocker cover resembles the knuckles of a closed fist. It was only manufactured between 36 and 47, also receiving the model name 61E due to its displacement: 61 cubic inches (1000 cc). And it was the engine that mounted the bikes that the brand sold just after the war ended. Another of its most outstanding features is that it was the first of the Harley engines to carry an oil pan.

With the end of the conflict, another of the most significant engines in Harley-Davidson's history appeared: the OHV Panhead. The rocker cover resembles a casserole upside down, hence its name. The heads in the Knucklead were made of steel, which made them overheated, hence in the Panhead they were changed to others made of aluminum. In addition, in this new engine, 1000 cc (model E) and 1200 cc (model F), both hydraulic elevators and oil pumps were also included for the first time to improve the lubrication system. It was a breakthrough. In fact, it is here that the story of Harley-Davidson's most colorful and great models begins.

The engine that came to replace the Panhead is the OHV Shovelhead, in 1966, which added more torque and power. In principle they are manufactured with a generator (‘Generator Shovels), in order to have alternators (Alternators) that considerably improve their efficiency. Two of Harley's most iconic models, such as the Electra Glide and FX Super Glide, were equipped with Alternator.

At the beginning of the 80's another engine was even more improved, which was manufactured until 1999: the Blockhead or Evolution, of 1340 cc. It has alloy cylinders, which together with the blades, allow better cooling. The valves also advance, as well as the combustion chambers, in order to comply with the gas emission law. After a few years the direct injection system is incorporated and thanks to a new floating frame the engine vibrates to a lesser extent.

Opening the 21st century, Harley opens the Twin Cam 88 engine, 1450 cc, with better resistance to high temperatures thanks to its many cooling fins, and that includes better lubrication. But above all, the difference with the previous one was that it included a double camshaft (DOHC) at the end of the crankshaft. Some argue that this engine appeared not to replace the applauded Evo, but to correct a patent issue that made this successful engine unprotected.

Another of the latest engines created by Harley is the Revolution, developed in conjunction with Porsche engineers. It is a V-Twin at 60º, 4-stroke, 115 hp and 1130 cc., The first to carry ESPFI, which was released, of course, by the muscular models of the V-Rod range in 2002.

The peculiar sound of a Harley-Davison's engine is, for many, heavenly music. So much that some people resemble that of a brotherhood during Holy Week: pom, pom, poropopom, pom, pom ... Others compare it to the 'pop pop' that is heard when we make popcorn ... And for romantics, it sounds like the Same human heart beat.

Be that as it may, it is evident that it is a unique, almost hypnotizing sound, that some of us put on the spiky hair, and that even the legendary Milwaukee firm has tried to register as a patent, without much success indeed.

What makes a Harley-Davidson sound so different from other motorcycles is nothing but the design of its engine. Like any normal engine, the Harley engine also has two pistons. The difference is that the crankshaft has only one elbow in which both pistons meet. This, combined with the “V” position of the 45º cylinders, produce intervals that give rise to that characteristic sound.

Today we propose to go beyond that unique melody and learn a little more about the history of the Harley-Davidson V-Twin and the engines that precede it.

Harley-Davidson's initial engines offered very little power, unable even to climb a simple slope. In fact, the first motorcycle of the brand had 175 cc, a power of 1.5 hp and a cylinder of 54 mm. Both that first Harley-Davidson prototype and the next two were tested on a bicycle chassis. They were designed to participate in races, but ended up functioning as rotor propellers for boats.

It was in the spring of 1903 when in that Milwaukee shed Harley and Davidson managed to manufacture an improved engine, to place it in a stronger and larger chassis, that of model number 1. It was an open secret that this engine was based on the one designed in France by Dion and Bouton in 1894. The displacement now reached 400 cc, with a cylinder of 74 mm and a power of 3 hp, a power capable, now yes, of ascending slopes. This motorcycle had a total of 5 owners and managed to travel the negligible figure of 163,000 km without major damage.

The company begins to market its motorcycles and it is in 1906 when the firm changes black to a new tone: gray. It is the birth of the slender Silent Gray Fellow, with a power of 4.3 hp in a 500 cc engine.

In 1909, Harley-Davidson presented its V-Twin engine, with a very particular sound and vibration response, installed on the 5D model. The 6.5 hp of power were given by its displacement of 810 cc. A new cylinder was added to the only one of the previous model, with the idea of ​​improving the speed of rotation, even at low revolutions. Thus, with two cylinders operating alternately, the torque remained constant, considerably reducing vibrations.

The two cranks, which went to a single reinforced crankshaft, in turn attached to the flywheel, were its main feature. It also drew attention to the fact that their rockers and rods were left in the air, totally visible to everyone. However, it was not a simple engine to start, because of its compression ratio, and the transmission belt did not work well, so that the motorcycle was withdrawn from the market, while they continued selling their machines with the previous single-cylinder engine.

Although most believe that the Harley-Davidson invented the two-cylinder engine, it is not entirely true. It was not a novel engine for the world of motorcycling, since in Europe, the Grifon, already used it long before on their motorcycles, like its biggest competitor, the Indian, so it was a trend at the time.

It would soon appear a new engine, the F-Head (F in the head). In 1911, the inconvenience of the rear belt is solved with a roller system and now also changes the arrangement of the valves, the intake in the cylinder head, and the exhaust gas, just next to the head.

This is how Harley-Davidson definitely enters the world of racing, even winning some as important as the Tourist Trophy on the Isle of Man, with the Stock Racer 6E. With the victories, the American firm gains notoriety, but also great technical improvements. The 7D and 8E models are born, the latter with a 988 cc F-Head engine; the 10, with kickstarter towards the front, and the J, with 1000 cc.

The W Sport Twin (1919-1923) was the engine that Harley-Davison manufactured for its racing bikes: WF model, with magnetic ignition, and WJ model, with electric system. Its main feature was that the cylinders were arranged in the direction of travel. It had 600 cc of power and also had a primary transmission system by helical sprocket.

Another of the distinctive characteristics of the Harleys, the tear shape of the fuel tank, also arises at this time, specifically in 1920. And at the end of the decade the engine there is a considerable evolution of the F-Head engine, until 1200cc

However, also in 29 curiously, another different engine appears again: the Flathead (flat head), which mount their new V74 models. This third generation engine no longer shows its moving parts. Seesaws and rods change places to be placed on the sides of the cylinders instead of on the head, which is now transformed into a combustion chamber. There were different versions of this engine, as well as several displacements: VL, VM, VLM, D. The latter stood out for having a vertical generator placed in front of the engine, right next to the cylinders, hence this type of Harleys popularly known as "the three cylinders".

During World War II, following the appearance of the BMW and its advanced two-cylinder boxer engines, Harley replied by imitating the German R12 with the XA boxer engines (1942-1943), to ride the motorcycles of the US Army, which They subsequently had their civil version. Harley-Davidson stopped using the Flathead engine for its two-wheeled bikes, keeping it exclusively for sidecar bikes until 1973.

The OHV Knucklehead (Knuckle Head), contemporary to the Flathead, is another of the mythical engines of the Milwaukee firm. It is named this way because the rocker cover resembles the knuckles of a closed fist. It was only manufactured between 36 and 47, also receiving the model name 61E due to its displacement: 61 cubic inches (1000 cc). And it was the engine that mounted the bikes that the brand sold just after the war ended. Another of its most outstanding features is that it was the first of the Harley engines to carry an oil pan.

With the end of the conflict, another of the most significant engines in Harley-Davidson's history appeared: the OHV Panhead. The rocker cover resembles a casserole upside down, hence its name. The heads in the Knucklead were made of steel, which made them overheated, hence in the Panhead they were changed to others made of aluminum. In addition, in this new engine, 1000 cc (model E) and 1200 cc (model F), both hydraulic elevators and oil pumps were also included for the first time to improve the lubrication system. It was a breakthrough. In fact, it is here that the story of Harley-Davidson's most colorful and great models begins.

The engine that came to replace the Panhead is the OHV Shovelhead, in 1966, which added more torque and power. In principle they are manufactured with a generator (‘Generator Shovels), in order to have alternators (Alternators) that considerably improve their efficiency. Two of Harley's most iconic models, such as the Electra Glide and FX Super Glide, were equipped with Alternator.

At the beginning of the 80's another engine was even more improved, which was manufactured until 1999: the Blockhead or Evolution, of 1340 cc. It has alloy cylinders, which together with the blades, allow better cooling. The valves also advance, as well as the combustion chambers, in order to comply with the gas emission law. After a few years the direct injection system is incorporated and thanks to a new floating frame the engine vibrates to a lesser extent.

Opening the 21st century, Harley opens the Twin Cam 88 engine, 1450 cc, with better resistance to high temperatures thanks to its many cooling fins, and that includes better lubrication. But above all, the difference with the previous one was that it included a double camshaft (DOHC) at the end of the crankshaft. Some argue that this engine appeared not to replace the applauded Evo, but to correct a patent issue that made this successful engine unprotected.

Another of the latest engines created by Harley is the Revolution, developed in conjunction with Porsche engineers. It is a V-Twin at 60º, 4-stroke, 115 hp and 1130 cc., The first to carry ESPFI, which was released, of course, by the muscular models of the V-Rod range in 2002.