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Difference between revisions of "Harley-Davidson Evolution"
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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-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 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. | ||