Cycle News - Archive Issues - 1980's

(Above) The new 883 Sportster retains the same styling of last year's stripped-down XLX-61. (Below) Biggest engine changes are aluminum cylinders and heads; the old 1000cc engine has been discontinued. The H~rley·Davidson 883 Evolution Sportster By Jim Wolcott It was just two years ago that Harley announced their Evolution engine: a 1340cc OHV air-cooled descendant of the timehonored Shovelhead engine. When this 28 model was introd uce d , H arl ey representatives . h inted tha t a sim ilar evo l u tionary powerpl ant wou ld someda y appear for wh a t was onc e H arley's perfor- mance kin g: the Sportster. That som eday has arrived. and the new 883cc Evolution Sportster is. no w in deal er's showrooms as a n ea rly-release 1986 model. The Sp ortster has been with us a long time. Harley-Davids on's overhead- valve unit-constructi on lightweigh t V-twin can trace its roots back to 1957, wh en th e 57 cu bic-inc h XL Sports ter replaced th e previous (and ill -fated ) 55 cu bic-inc h side -valve KH Spo rts ter. The OHV d esign was big new s in 1957; with it s magneto ig n ition a nd a dry weight o f 460 pounds, th e XL Sportster was widely regarded as a state-of-the -art mo to rcycle. Shortly after AMF acq uired HarleyDavidson in 1969, the Sportster was enlarged 10 61 cu bic- inc hes (1000cc), a nd a n elec tric sta rte r was introd uced on the XLI 000 model. T he Sportster 's h igh- performan ce image had fad ed wit h th e introd uct io n o f lighter a nd more powerf ul mac hines fro m Britain and Japan: in the 1970s the engi ne - sti ll eq uipped with cas tiron cylinders a nd cyli nder hea ds saw only minor changes. Wo rse, horsepower and relia bility were still not topics o r co nversation among Sportster ow ne rs. When Harley-Davidson parted from AMF in 1980, both th e Sp ortster a nd the Sh ovelhead were sched u led for u pda ting and revisio n. Because it was more sensi tive to th e stead ily decreasing q ua lity o f gasoli ne, and it was more co m mo nly used for heavyweigh t touring and sideca r use, th e Shovelhead was the fir st engine to a p pear as an Evolution model. As with the larger Evolution engine, th e Evolution Sportster was enginee red as a revision of a n existing design , ra ther tha n as a ne w motorcycle from th e ground up. According to Harley. th e new engin e/transmission unit has 426 parts (co u nting nuts, bolts a nd fast eners), of which 206 are new a nd different from last yea r 's Sportster . In the process, th e weight of th e engine/transmission package has been trimmed from 195 pounds to 186.8 pounds. T he cran ksha ft is made of two forged -steel flywheel s with integral mai ns hafts. The rod journal fits between th e flywh eels, a nd is secured by two large nuts. As wi th the previous engi ne , th e two rods share the same journal, with the same fork-and -spade configuration. Stroke is unchanged at 96.8mm. The connecting rods are 0.50-inch shorte r than tho se o f the old engine, and ar e the same forged-steel units ori gina lly developed for th e highperformance XRIOOO.· The big end runs in roller bearings, and the small end is fitted with bushings. The pistons are engineered by th e German firm JSG (thoug h actua lly manufactured in Wisconsin ), and feature th e sa me conical-oval profile of th e big-inch Evolution engi ne.. The sli ght barrel shape o f the skirt helps to trap a wedge of oil as th e piston descends, allowing for tighter piston clearance and improved cooling. T h ree piston rings are fitt ed : the two top rings a mere 0.057-inch wide: with the double-rail oil-control ring measuring 0.107-inch. Where the old Sportster used domed pistons and a hemispherical combustion chamber, the new pistons have flat tops with shallow cut-outs for valve clearance. The l340cc Evolution engine had D-shaped combustion chambers, but further experiments with that contour have concluded that more power is available with an oval-shaped chamber: the shape used for the new Sportster powerplant. The old engine invited detonation, with its spark plug mounted on the side of the hemispherical chamber; the new head positions the plug at the junction of the intake and exhaust valves. In spite of the superior combu stion ch am ber and improved flame trav el; the compression ratio was only u p pe d from 8.8: I to a conse rva tive 9.0:1. Cylinder bore has been reduced from 81mm to 76.2mm. with th e sma lIer bore acco u nting for th e redu ced e ngi ne d ispla cemen t. The finned a lu mi n um cylinder is cast around an iron lin er, and incorporates Harley's unique "Spiny-Lok" ribbedper im eter iron liners ; the ribs help to a nchor th e liner to th e casti ng and im prove heat transfer. 'T he cyl inde r heads closely resem ble th ose o f th e larger Evolu tio n engine, and incorpo rat e simi la r th reetier rocker-boxes. T houg h the Sportster 's head is a differe nt cas ti ng, it .sha res th e sa me included valv e a ng le a nd spark plug location: differences are in a va lve a nd port size. From a ma n ufactur ing standpoint, since th e two head s share ma ny cri tica l a ngles and dimensions, the Spor tster a nd I340cccylinder heads are actually machined on the same assembly line substa ntialIy tri mmin g production costs. T he exha ust val ve is made of two p ieces, welded together abo u t midwa y up th e stem. A special heatres istant steel is used fo r th e val ve head, a nd the faci ng is finish ed with grade-six Stell ite for co mpa rability wit h u nleaded fuel. The in take valve is a one -piece un it without StelIite. Both th e Sportster a nd 1340cc Evolutio n engines use the same (mea ning intercha ngeable) valve springs, collar s, keepers, seals and valv e guides. Also interchangeable between the two engines are the hydraulic valve lifters. The new Evolution Sportster uses th e same gear-driven four-camsha ft system as the previous Sportster, th ough th e cas ing has been lengthened 0.25-inch to accommodate the h ydraulic system. The new lifters eli mina te the valve adjustment ritual for th e Sportster, which, since the push rods were buried behind the exhaust cross -over pipe, wa s always an awkward and time-consuming affai r . T he Sportster 's co m p lex four-camshaft des ign has always been a tuner's nightmare; selecting and fitting gears with minimal lash and precise timing was problematic at best. For the

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