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How Harley-Davidson Works

A Basic Motorcycle Today

Two things worked in concert with each other to make motorcycles look so large today:
  1. 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.

  2. 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.

a Harley-like custom motorcycle
Today's motorcycles are very distant relations to the motorized bicycles of the past.

This motorcycle is not a Harley -- it is a Harley-like custom motorcycle that strips a modern motorcycle down to its bare essentials. For example, this motorcycle has an engine and a transmission:

the two-cylinder V engine of a Harley-like custom motorcycle
88 cubic-inch (1,450 cc), two-cylinder V engine

the exhaust pipes of a custom motorcycle
The stainless steel exhaust pipes are connected directly to the engine's cylinders.

In this case the engine is an 88 cubic-inch (1,450 cc), two-cylinder engine. The cylinders are arranged in a V configuration with a 45-degree angle to the V. The engine uses dry sump lubrication, and the external tank for the oil mounts above the transmission. Exhaust is simply a pair of stainless steel pipes connected to the exhaust port of each cylinder. There is no muffler or catalytic converter of any kind.

The transmission sits just behind the engine. It is a 6-speed sequential manual gearbox. The engine transmits its power from the crankshaft to the transmission through a primary drive. The power then moves from the transmission to the rear wheel through the final drive, which in this case is a chain as seen in this photo:

the final drive of a custom motorcycle
The primary drive on this motorcycle is a very wide Kevlar/rubber belt. The large chain is the final drive.

All the engine's power ends up going to the back wheel.

motorcycle back wheel
The engine's power ends up going to this extremely wide back wheel.

You can also see the rear disk brake, as well as the back portion of the frame. In the above photo, as well as the photo below, it's obvious that motorcycle frames can be extremely simple.

a motorcycle frame
This motorcycle frame has a simple design. Because it has no rear suspension, it is called a "hard tail."

The frame is just a few steel tubes bent and welded together. See this page for photographs of several different frames. This motorcycle has no rear suspension and is therefore called a hard tail.

The front fork, the only suspension component on this bike, is located at the front end of the motorcycle.

motorcycle front fork
The front fork is the only suspension component on this bike. It can compress to act like a shock-absorber.

You can see that the front wheel is much smaller than the rear. There is a single disc brake at the front. The front fork can compress to absorb shock. At the top of the front fork are the handlebars and headlight.

Certainly this motorcycle is not as simple as the first Harley-Davidson in 1903, but it is not super-complicated either. This is minimalist gasoline-powered transportation. So, how does a Harley compare to this basic-bike? Let's take a look.