The SX 350 is the enduro or street scrambler version of the Sprint SS 350. Motorcycle Classics gives 1971 to 1974; bikesales gives 1969 as the start, together with the SS. It was built in Varese by Aermacchi-Harley-Davidson and sold mainly in America.

The first model (1971) has the open spine frame of the Sprint, a 19-inch front and 18-inch rear wheel with knobbly tyres, a smaller tank, no rev counter, high bars with a cross brace and a high exhaust. Gear lever on the right, kick-starter on the left, four-speed box and Ceriani forks, which Cycle Guide praised in 1971.

Then came the updated model with a double cradle frame, 12 volts, an electric starter and left-foot gear change. Sources disagree on the year: Motorcycle Classics and Bike-urious say 1972, while Tanshanomi, The Classic MotorCycle and Shannons say 1973. Cycle News tested an SX with starter in April 1973.

According to Motorcycle Classics some 11,000 Sprints of all types were sold in 1973–1974. After that the 350 four-stroke disappeared; Harley carried on with two-strokes.

SX 350 (1971–c. 1972): spine frame, 6 volt, kick-start only, c. 141 kg dry. SX 350 (c. 1972/73–1974): cradle frame, 12 volt, starter motor, left-foot gear change. Cycle News called the later model very heavy in 1973 at about 180 kg (400 lb). The sister models are the SS 350 (road) and the Sprint 250.

The engine itself is strong; Tanshanomi calls them durable. The weak points are around it. The bike is heavy and has a high centre of gravity. After a few days standing it sometimes needed a push start. The rear shocks are too stiff, and on the early model the engine and low exhaust parts are unprotected.

For the late model sources mention mediocre brakes, cheap frame fittings and poor quality control. According to Pipeburn the electric starter never really worked well. Cycle News reported sticking forks in its 1973 test. An engine rebuild requires knowledge that has become rare.

In general for the 350 Sprint: difficult hot starting, a heavy dry clutch and vibration that can shake bolts loose.

Many engine parts are the same as on the SS 350. Jan Willem Boon in Ruinen (NL) sells new old stock labelled “Sprint, SS, SX 350 1969–74”. The American specialist Moto Italia has been sold and is temporarily not taking orders. According to Tanshanomi parts now mainly go through the network of riders and clubs.

Price indications (sale prices unless stated otherwise):

• Motorcycle Classics (2013): value $2,400–4,500.
• Mecum (USA, January 2017): 1974 SX 350 for $5,500.
• Mecum (USA, September 2023): 1973 SX 350 for $3,000.
• Car & Classic (August 2026): 1973 SX 350 in France, asking €7,000.

So prices in America are lower than asking prices in Europe.