| MODEL | HARLEY-DAVIDSON X-90 SHORTSTER 1973 - 1975 |
| Year | 1973 - 1975 |
| Engine Type | Two-stroke, single cylinder, piston port |
| Displacement / Capacity | 90.5 cc / 5.5 cu in |
| Bore X Stroke | 48 x 50 mm |
| Compression Ratio | 9.22:1 |
| Cooling System | Air cooled |
| Max Power | 6 kW / 8 hp |
| Max Torque | — |
| Ignition | — |
| Induction | — |
| Start System | Kick |
| TRANSMISSION SPECS | |
| Lubrication | Oil injection (separate oil tank) |
| Gear Box | 4-speed, foot shift |
| Clutch | Wet multi-plate, hand operated |
| Final Drive | — |
| CHASSIS SPECS | |
| Frame | Steel tubular backbone |
| Front Suspension | — |
| Rear Suspension | — |
| Front Brakes | Drum |
| Rear Brakes | Drum |
| DIMENSION SPECS | |
| Overall Length | — |
| Overall Width | — |
| Overall Height | — |
| Seat Height | — |
| Wheelbase | Just over 1016 mm / 40 in |
| Ground Clearance | — |
| Dry Weight | — |
| Wet Weight | — |
| WHEEL SPECS | |
| Front Tyre | 3.00 x 10 |
| Rear Tyre | 3.00 x 10 |
| FUEL SYSTEM | |
| Fuel Capacity | — |
| Fuel Consumption | — |
| Top Speed | — |
The X-90 was a street-legal 90cc minibike built in Italy by Harley's Aermacchi subsidiary during the AMF years, aimed at the youth market Honda's Monkey bikes were winning. It paired a piston-port two-stroke single with oil injection and a four-speed foot-shift gearbox in a small steel backbone frame on 10-inch wheels, with lights so it could be ridden on the road. It sold reasonably but never threatened the Japanese minibikes, and it disappeared after the mid-1970s.
