Harley-Davidson Evolution engine

It was made in the 1,340 cc (82 cu in) displacement for Harley-Davidson Big V-twins bikes, replacing the Shovelhead engine until 2000 when the last EVO was placed in a production factory custom FXR4 (FXR2 and FXR3 were the first CVOs).

Harley-Davidson's official name for the engine was likely related to the company's attempt to reform its image following the 1981 management buyout from previous owner American Machine and Foundry (AMF).

The unit construction of the Harley-Davidson Sportster, which has essentially been unchanged since its inception as the side-valve 750cc "K" Model in 1952, was retained with the Evolution engine upgrade in 1986, resulting in a unique valve train configuration.

This configuration is friendly to radical, high-output cams, making the Sportster Evolution a natural choice for the once Harley-Davidson owned line of Buell Motorcycle Company sportbikes from 1986 up to late 2009 (2010 model year).

[4] Carburetors were standard on Sportster engines until 2007, when they were replaced by the Delphi Electronic Sequential-Port Fuel Injection (ESPFI) system.

The Big Twin has been accompanied by a number of different primary drives and transmissions, both on production Harley-Davidson motorcycles and in custom applications.

Harley-Davidson Evolution engine at the Harley-Davidson Museum
Above, a color-coded approximate diagram of the Sportster Evolution valve train superimposed over an image of a Sportster Evolution. Crank output is purple; cams are red; pushrod/lifters are yellow; rockers are blue; valves are dark green, with seats shown in light green.