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Bike of the Month
March 2022
1975 Harley-Davidson SX 250
By Frank Vavra

Added to my stable of fine mounts is a 1975 Harley Davidson SX 250. This is a pristine example of a Harley (Aermacchi manufactured) off road machine.

The SX250 is powered by an air-cooled, 2-stroke, single-cylinder engine with oil injection. A 32mm Dell ‘Orto PHB32 carburetor fed the piston-ported, chrome-plated cylinder, while a capacitive-discharge ignition provided sparks. Drive to the wet multiplate clutch was by gears, and a 5-speed transmission and chain to the rear wheel completed the drivetrain. The engine fitted into a dual-cradle steel tube frame with a Ceriani-style front fork and swingarm rear controlled by a pair of spring/shock units with five adjustable preload settings. Tires were 3.25 by 19 inches front and 4 by 18 inches rear.

Though conventional in most ways, the SX250 incorporated a number of useful features. The ignition system was independent of the battery, so the engine could be started and run without one. The swingarm used snail cam adjusters (a scheme pioneered by Rickman Motorcycles in England), making it easier to accurately set rear wheel alignment in the field. Equally practical was the quick-detachable rear wheel for fast tire repairs. Oil for the pressure-fed lubrication system was carried in the top frame tube; and the kickstart lever drove through the primary, meaning the engine could be started in gear — a real boon in the dirt.

The result was a machine that could be made competitive in offroad events with the right upgrades. Enduro legends Larry Roeseler and Bruce Ogilvie used a highly modified SX250 to win the motorcycle class in the 1975 Baja 500, recording Harley-Davidson’s only win ever in that event.



    • Engine: Two-Stroke Single

    • Type: Air-Cooled, Port Induction

    • Bore & Stroke: 61mm x 60mm / 2.40″ x 2.34 Inches

    • Displacement: 174.1cc

    • Compression Ratio: 10.7 : 1

    • Carburetor: 27mm Dell’Orto

    • Electrics: 12 Volt

    • Lubrication: Oil Injection

    • Starting: Kick Only

    • Horsepower: 17HP

    • Transmission: 5-Speed

    • Primary: Gear Driven

    • Clutch: Wet, Multi-Plate

    • Frame: Steel, Double Down Tube

    • Suspension: 32mm Marzocchi Fork / Swingarm, Twin     Shocks

    • Wheels/Tires: 3.00 x 19 / 3.50 x 18

    • Brakes: 140mm SLS Drum / 140mm SLS Drum

    • Weight: 247 Pounds

    • Wheelbase: 54 Inches

SX250 left.jpg
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