Between the First and Second World War, the Paris factory of Gnome et Rhone moved from aircraft engine production to building a variety of motorcycles with single cylinder and flat-twin engines of up to 750cc (Gnome et Rhone motorcycle). After 1945 Gnome Rhone built a few small capacity two-strokes, it didn't survive the 1950s. More specs and user manual of Gnome motorcycles you can see in next overview.
Gnome et Rhone
Gnome et Rhone review