I think it is a Junak M10

CCO Public Domain Image

Junak is a brand Polish motorcycles, the only four-stroke models produced in Poland between World War II and Revolutions of 1989. The name literally means "brave young man". Produced by Szczecińska Fabryka Motocykli (SFM) (en.: Szczecin Factory Motorcycles) in three variants: M07, M10 and B20.