Atmospheric engines can be identified by the naked, unfinned cylinders linked to a single carburettor — although you would be very fortunate indeed to find one as only 27 were known to be produced, and even fewer survive. A simple yet powerful engine, effectively two singles on a common crankshaft and cases, the 45 degree cylinder configuration was hugely significant, the birth of a classic design that endures to the present day in the Harley-Davidson line-up.
The major innovation of the design was the mechanically operated inlet valve, activated by a pushrod from the camshaft, allowing engine revs and power to be increased substantially from earlier models. After continuous improvement over nearly 20 years, by the F-Head was achieving 24hp from cc — cutting edge for motorcycle engines of the time.
The F-head motor can be identified by the single external pushrod actuating the inlet valve, which sits on a distinctive valve cage atop each cylinder head. The Flathead is a simple, robust and reliable side-valve engine, originally cc but increasing in capacity to cc in The engine was used until in the motorcycle range and, remarkably, from until in the three-wheeled utility Servi-Car — a span of 42 years and a real testament to the reliability of the design.
Flathead engines were popular because they offered a simpler design with easier repairs and servicing than overhead valve designs, an important consideration at the time for many owners. The Flathead motor was also highly successful in racing and in the K-series bikes — later to evolve into the Sportster — introduced to compete against lightweight, sporty motorcycles from the UK and Europe.
Flathead motors can be easily identified by the finned flat cylinder heads, which bolt directly to the barrels — the valve gear is set off to one side, typical for side-valve engines. The first v-twin Harley-Davidson engine with overhead valves and a recirculating oil system, the Knucklehead got its name from the rocker boxes, which are said to resemble a pair of human fists with the knuckles sticking out.
The Knucklehead is still considered by many to be the best-looking Harley-Davidson engine ever produced and early Knuckleheads reflect this in their high value to collectors. Design and manufacturing innovations driven by WWII included internal oil lines, new aluminium cylinder heads replacing the cast iron of its predecessor, and hydraulic valve lifters to minimise the fiddly task of manually adjusting the valve clearances.
Named, as with previous models, for after the distinctive rocker covers, the Shovelhead was initially introduced as a cc model. The all-aluminium engine was a quantum leap forward in design and reliability for Harley-Davidson and is widely credited with saving the company as it emerged from ownership by the AMF conglomerate.
The end product of seven years of development, the Evo addressed many of the issues of the Shovelhead — it was more reliable, quieter and with less vibration, using significantly less fuel and generating more power than its predecessor. Squish-band combustion chambers, flat topped pistons, stronger con rods and valve train, a redesign oil system and a computerised ignition system were innovations that meant the Evo also ran cooler and was virtually oil-tight. The Evo engine is distinctive thanks to its all-aluminium construction and the block-like plain aluminium rocker covers.
The massively successful Evo engine evolved into the Twin Cam 88 for 88 cubic inches, or cc for the model year, named for the two chain-driven cams driving the valve system. Mobile Newsletter chat subscribe. Motorcycle Models. About Harley-Davidson. How Harley-Davidson Works. When someone mentions the words "Harley-Davidson" several things come to mind: The company that produces motorcycles.
The actual motorcycles that the company produces. The history and tradition that surround the company and the products. Next Up. Motorcycle Image Gallery. A Basic Motorcycle Today Two things worked in concert with each other to make motorcycles look so large today: The engine grew bigger and bigger, so the motorcycle grew bigger to hold the engine and support the weight. As the motorcycle grew heavier, the wheels and tires got bigger and stronger to support the weight, as did the brakes, the frame, etc.
The fuel tank also expanded to give the larger engine the fuel it needs. With growing engine sizes, motorcycles became much faster and could travel much longer distances. Higher speeds meant the addition of a transmission. Rider comfort in the form of bigger tires, suspension systems, seats and so on were added to make the ride better. Additional speed also makes the tires more important for performance, so the tires got wider.
You can see all of the advanced motorcycle features in the motorcycle pictured below. For example, this motorcycle has an engine and a transmission: 88 cubic-inch 1, cc , two-cylinder V engine The stainless steel exhaust pipes are connected directly to the engine's cylinders.
All the engine's power ends up going to the back wheel. What is a Harley? Here are some of the distinguishing characteristics of the engine: Until , Harley-Davidson had been devotedly married to the two-cylinder V-twin design with a degree angle between the cylinders.
The engines are air-cooled. The engines have overhead valves that are activated by camshafts in the crankcase. Oil comes from a dry sump lubrication system. Harley engines have a long stroke. This means that the engines are low-revving and have lots of torque.
Redline is typically in the 5, RPM range. Harley engines have a single-pin crankshaft, giving these engines a unique sound. We'll have more on that distinctive sound in the next section.
Next, we'll learn about the Harley mystique and its distinctive sound. Think about a Marlboro cigarette. It's simply a bit of tobacco wrapped in paper. There are hundreds of other brands of cigarette that are nearly identical, but the Marlboro brand has mystique.
Part of it comes from image advertising, but the other part is cultural. The people who smoke Marlboro cigarettes tend to be a certain type of person. Because they advertise and reinforce the brand image, they in turn attract more of their kind to the brand -- and so on. In the case of Harley-Davidsons, although some amount of advertising is done, far more of the brand image comes about in other ways: The use of Harleys in the movie and television industry. The huge Harley rallies that can attract over , bikers.
The people who ride Harleys, and the image they project in public. These elements along with a few others create a resonating, grassroots type of promotion that is extremely rare, but fascinating when it happens. This begins to convey the Harley mystique.
Now let's discuss something else that resonates -- the telltale Harley sound. Instead of one piston firing every degrees, a Harley engine goes like this: A piston fires. The next piston fires at degrees. There is a degree gap. A piston fires. And the cycle continues. Harley Engines We live in a world where computer technology changes on a daily basis.
Japanese motorcycle companies tend to create new engine designs every year. Car lines are completely revamped every three or four years.
Then there is the Harley-Davidson Motor Company. If you ignore the first few years of the company's history as a period of experimentation, there really have been only seven major engine revisions during the company's year existence: Flathead engines - Manufactured between and Flatheads did not have overhead valves. Facts About Icebreaker Ships. Facts about Trans-Siberian Railway. How is a Plane Constructed.
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To create this type of engine, the crankshaft has two separate pins for the connecting rods from the pistons.
The pins are degrees apart from one another. A Harley engine has two pistons. The difference in the Harley engine is that the crankshaft has only one pin , and both pistons connect to it. This design, combined with the V arrangement of the cylinders, means that the pistons cannot fire at even intervals. Instead of one piston firing every degrees, a Harley engine goes like this:. At idle, you can hear the pop-pop sound followed by a pause.
So its sound is pop-pop
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