Cycle News is a weekly magazine that covers all aspects of motorcycling including Supercross, Motocross and MotoGP as well as new motorcycles
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@)QQO GOCSU(JD®Q9o[Q)CSUWD@J~@)Ulf -W@)[]QD~D@) ~W® By Gary Van Voorhis Harley-Davidson's Evolution V 2 engine, introduced in the company's 80th year, is a major element in the ongoing program of product refinement at H-D. The idea moved from the drawing board lO the firsl sand casling of a lwo-piece · 8 f 1 f' rocker box In.197 ,.a ul lye years before mceptlon. Olher 24 components of the total machine package were also being developed and were incorporated into the product line as they became available. Vi bration isolating elastomer engine mounts, a five speed transmission, anti-dive ail front suspension, and computer designed chassis were all introduced prior to the engine's debut. Don Ballentine, Harley-Davidson's chief engineer for power trains, noted five characteristics as goals for the engine: "We wanted to have a reliable, serviceable, durable engine which would offer good performance while minimizing maintenance costs." The end result was the Evolution V' engine'which reaches peak' horse- power at 5,000 rpm versus 5,400 rpm for the current 8~ cubic lOch (I ,340cc) Shovel head engine and wetghs 18 to 20 pounds less. Horsepowerisclllimed to be up 10 percent while torque, in mid·range, is increased by 15 percent. Harley doesn't publish horsepower figures, but an informed estimate by a Harley dealer came up with a figure of "about 65 horsepower for the current 1,340cc engine," That would place the new engine in the 70 horsepower range. The Evolution V2 engine utilizes the same basic bottom-end as the Shovel head, but that's where the similarity ends. From the cam centerline up, the engine is new. Redesigned heads, pistons, valve train, rocker boxes, ignition module, camshaft plus aluminum cylinders with cast iron liners are featured in the package. Harley wanted things right and logged 750,000 miles of durability testing along with 5,600 hours on the dyno before they were satisfied. The engineers at Harley saw no reason to abandon the V-twin, twovalve head configuration which has worked so well for them. However, ,they were looking for ways to improve it. The result was the Side Squish Combustion Chamber (SSCC) and new valve geometry. The valves are now positioned at a 58-degree- included angle similar in valve geometry to those in Harley's XR750 racing engines. A bigher pon velocity and increased swirl effect, combined with the reduced dimensions of the SSCC and a new spark plug location closer' to the center of the chamber, produce a more efficient burning of the fuel mixture which is supplied via a 38mm carbu retor. The rocker box is a three-piece "sandwich" design and allows easy top-end access without removing the engine. The new flat-top pistons are made for Harley-Davidson by Mahle, a West, German company. "We used to manufacture our own pistons," said Ballentine, "but that's a very highly specialized field and I'm glad we're out of it." The piston is composed of highstrength l2-percent silicon aluminum with a conical-oval shape. Conicaloval, according to H-D, means the thrust side of the piston contour-the opposite plane from the wrist pin-is oval as well as barrel-shaped. Thjs variable ovality ensures a close pistonto-cylinder £it and also forms areas that allow the piston to ride on a wedge of oi'l which reduces friction, improves oil control and increases piston life. Reinforced connecting rods, for a substantial increase in rod fatigue strength, handle the 8.5: I compression ratio. The all-new cylinders combine the light weight of aluminum with the strength of cast iron, Deep-finned aluminum cylinders, made by highpressure die-casting methods, surround what Harley calls Spiny-Lok liners of cast iron, The Spiny-LoJ< design consists of 48 equally spaced lateral grooves located on the outer surface of the liner to allow a permanent locking bond between the cylinder and liner. The liners can be re-bored in increments up to ,03,0 over-bore for longer engine life. The engineers at Harley designed a new top-end fastener system which insures a minimal amouDtof cylinder