The first engine that William Harley ever designed was in 1901, before the Harley Davidson Company even began. It was a small engine that displaced 7.07 cubic inches and had 4-inch flywheels. This engine was designed to power a regular bicycle, however it did not give the bike enough power to ascend the hills of Milwaukee.
The next engine Harley developed with the assistance of the Davidson brothers was bigger and more powerful. This engine was 24.74 cubic inches with 9-3/4 inch flywheels weighing 28 pounds. The group also received help with this engine from outboard motor pioneer Ole Evinrude, and was much more successful, premiering the first Harley Davidson motorcycle in 1904 at a race in Milwaukee.
Since then Harley Davidson has continued to improve and develop their motorcycle engines. The Flathead engine was manufactured between 1929 and 1974. These engines did not have overhead valves. The valves ran alongside the engine and opened upward into a chamber beside the combustion chamber. A typical flathead engine displaced about 45 cubic inches and produced about 22 horsepower.
The Knucklehead engine was manufactured between 1936 and 1947. This engine was available in 60 cubic inch and 74 cubic inch variations, producing 40 to 45 horsepower.
The Panhead engine was manufactured between 1948 and 1965. This engine also came in 60 cubic inch and 74 cubic inch variations, but produced 50 to 55 horsepower. The biggest difference between the two engines was the aluminum heads on the panhead and internal oil lines, as opposed to external oil lines on the knucklehead.
The Shovelhead engine was manufactured between 1966 and 1985. This engine displaced 74 cubic inches and produced 60 horsepower.
The Evolution engine was manufactured between 1984 and 1999. This engine displaced 81.8 cubic inches and produced 70 horsepower. Some smaller evolution engines are still produced today, and are used in the Sportster line of Harley Davidson motorcycles.
The Twin Cam 88 engine began to be manufactured in 1999. This engine got its name because it has 2 cams in the crankcase to activate the valves. This engine displaces 88 cubic inches and produces 80 horsepower making it the largest production Harley Davidson engine. This engine is air-cooled and uses overhead valves activated by pushrods.
The Revolution engine began to be manufactured in 2001. This engine is currently only used in the VSRC model. This engine is quite different from the others produced by Harley Davidson. It is water-cooled instead of air-cooled. Its V angle is 60 degrees instead of 45 degrees. It has 4 overhead cams instead of two in the crankcase and it is fuel injected. This engine s smaller at 69 cubic inches, but it produces 115 horsepower due to its much shorter stroke.
Harley engines are big. They have a very distinctive sound. Once you know what a Harley sounds like you will always recognize when one is coming. The Harley sound is part of the whole Harley experience. The sound is enhanced by removing the muffler and comes from the way the engine is designed.
