The "locomotive" style headlamp nacelle was introduced on the XLH in 1959 and was used until 1966. The XL remained the standard model with a milder compression ratio. In 1958, the XL received new fenders and headlight nacelle, and ignition switch mounted on the left fork.Ī second model, the XLH, was basically the same bike as the XL, but with the "H" denoting a higher compression engine with larger valves. Making 40 horsepower and weighing 495 pounds, the 1957 Sportster XL was not yet burning up roads.
Later 900cc bikes had 9:1 compression ratio. Harley-Davidson had previously used aluminum heads on their Big-Twin Panhead motor, which helped reduce engine operating temperatures in warm weather.īut early Panhead riders experienced top-end problems, so the Motor Company cautiously chose cast-iron for the Sportster heads.Ĭoncerns of engine overheating kept the compression ratio of first-year Sportsters at a conservative 7.5:1. The passenger foot-mounts were also one-year only, as was the carburetor (Linkert DC-1).Īluminum is usually the preferred material for cylinder heads - not only is it lighter than cast-iron, it also dissipates heat better.
Intake valves were 1-11/16" for 1957 only. The first-year Sportster saw many changes during the production year, and have several unique features.Įarly 1957 models didn't have cylinder head rocker bushings like later models did, and used tappet rollers without needle bearings.
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