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Difference between revisions of "Harley-Davidson Evolution"
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→Evolution on the Sportster
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==Evolution on the Sportster== | ==Evolution on the Sportster== | ||
[[Image:Harley_V-twin_w_valvediagram.jpg|thumb|Above, a color-coded approximate diagram of the Sportster Evolution valvetrain 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.]] | [[Image:Harley_V-twin_w_valvediagram.jpg|thumb|Above, a color-coded approximate diagram of the Sportster Evolution valvetrain 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.]] | ||
The quasi- | The quasi-unit construction of the Harley-Davidson [[Harley-Davidson Sportster|Sportster]], which has been part and parcel with the highly-successful model line since its inception, was retained with the Evolution engine upgrade in 1986, resulting in a unique [[valvetrain]] configuration. Unlike almost any other engine in production today, the Sportster Evolution uses one cam per engine [[overhead valve]], resulting in four individual, single-lobe, gear-driven [[camshafts]]. The cam lobes are thus all located one behind another, and [[pushrods]] are arrayed in parallel fashion as a result. This allows each lifter and pushrod to deflect from the cam lobes perpendicular to the lobe plane. This configuration is friendly to radical, high-output cams, making the Sportster Evolution a natural choice for the [[Harley-Davidson]]-owned line of [[Buell]] [[sportbikes]] from 1986 up to 2003. | ||
The Sportster Evolution engine has remained largely unchanged from 1986 to 2006, though changes to the transmission, final drive and motor mounts have necessitated changes to the Sportster Evolution case. Construction is almost entirely the same between 883 cc and 1200 cc versions; the chief difference between the two is a much smaller bore on the 883 cc, along with slightly different heads. Conversions from 883 cc to 1200 cc are relatively inexpensive and commonplace. Until 2007, all Sportster Evolution engines (and in fact, all Sportster engines of any kind) were only built with carburetors; today, however, all new Sportster models come standard with [[fuel injection|fuel-injected]] Evolution engines. | The Sportster Evolution engine has remained largely unchanged from 1986 to 2006, though changes to the transmission, final drive and motor mounts have necessitated changes to the Sportster Evolution case. Construction is almost entirely the same between 883 cc and 1200 cc versions; the chief difference between the two is a much smaller bore on the 883 cc, along with slightly different heads. Conversions from 883 cc to 1200 cc are relatively inexpensive and commonplace. Until 2007, all Sportster Evolution engines (and in fact, all Sportster engines of any kind) were only built with carburetors; today, however, all new Sportster models come standard with [[fuel injection|fuel-injected]] Evolution engines. | ||