Before Harley-Davidson bought controlling interest in Aermacchi, this “sloper” engine powered a variety of light weight Aermacchis including the stylish Chimera, a 175cc version also on display in the Museum.

In 175, 250 and 350cc versions, for street, off-road and racing of many forms, this was a true workhorse for Aermacchi, and later Harley-Davidson.  From mild street bikes to championship winning dry-clutch dirt track and road race machines of 250cc’s, this single was remarkable. It still works well in vintage racing.

This Sprint version is the SX350, a middle-weight with off-road or “enduro” styling popular in America at the time. The braced handlebar, upswept exhaust and an optional skid plate helped attract a new audience, but the machine did not fare well against the foreign competition in showrooms.

In the 1960’s Americans were introduced to a wide range of new middle weight imported motorcycles. Harley-Davidson offerings were by then all roughly 900cc and larger machines, heavy weight and relatively expensive. Seeking a quick fix for the market share they gave up to foreign makers, Harley bought a controlling interest in Aermacchi about 1960. With this arrangement machines with displacements ranging from 50cc’s to 350cc’s became available in two-stroke and four-stroke models including those commonly referred to as Harley-Davidson Sprints, and about 50,000 were imported over a period of 15 years. The SX350 got a major chassis redesign in 1972 and 350 model lasted through 1974. In 1978 the Castiglioni brothers bought what remained of the Aermacchi factory and equipment.

This 350SX Sprint with a striking custom paint job resides in the Harley-Davidson section of the National Motorcycle Museum alongside a wide range of Harleys of all types, 1908 to the early 2000’s.


    • Engine: Air-Cooled Single
    • Type: Four-Stroke, OHV
    • Bore & Stroke: 74 mm × 80 mm
    • Displacement: 344cc’s
    • Compression Ratio: 9.3 : 1
    • Ignition: Battery, Points, Coil
    • Carburetor: Dell ‘Orto
    • Starting: Kick
    • Horsepower: 25
    • Primary: Gear Driven
    • Clutch: Dry, Multi-Plate
    • Final Drive: Chain Driven
    • Transmission: 4-Speed
    • Frame: Spine / Tubular Steel
    • Suspension: Hydraulic Fork / Swingarm, Dual Shocks
    • Brakes: Drum Front / Drum Rear
    • Wheelbase: 56 Inches
    • Wheels / Tires: 3.00 x 19 /. 3.50 x 18
    • Weight: 315 Pounds
    • Top Speed: 80 MPH, Approximately
5 replies
  1. DeSoto Jason
    DeSoto Jason says:

    Learned to ride on one of those in a field behind our house in Perth Amboy NJ. My buddy Georgie & I jumped it on a little plywood ramp we made until we bashed in the front fork hitting a pile of rocks! Sold it to a kid who fixed it!
    We saw him a few weeks later walking down the street with a bandage on his face and nose. Asked him what happened. He told us he started her up & then did a standing burn out, let the clutch out flat footed, it popped a wheelie and broke his nose with the tach!! We literally fell on the ground laughing!! Best memories, for us anyway!! 🤣😎

    • Hector
      Hector says:

      This bike has a verdict paint job and seat. Find another that has the same, it’s obvious you haven’t been to the museum you would have seen worst.


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