harley made all kinds of weird stuff from snow mobiles to motorhomes i even have a harley 3 wheeled golf cart most of that stuff came in the amf years the scooters were produced from 1959 to 1965 and were 165cc even came with a side car option but i only know this stuff because my boyfriend is a certified HD mechanic and he tells me all this stuff lol
Doesn't surprise me that Harley would have produced something like that back in the day. Any company that makes an engine for one thing has often made an engine for something else at one point in time.
When I was 12, my grandpa bought me a 1979 Honda Express II moped from a Mexican flea market for only $200. I loved that thing dearly.
It looked just like this, only mine had orange wheel wells.