Scooters were HUGE in that period. There were dozens of brands. Vespa and Lambretta were the biggest, but most of the major motorcycle companies had scooters. Not just Harley, but there were scooters from Triumph, BSA, Velocette, Ducati, Moto Guzzi, Zundapp, Maico, and on and on. Most scooters were 2-strokes, but not all.
The Harley Topper was a 165cc, 2-stroke, with a rope-pull starter.
PhilB