Having rider and worked on my BMW R65. It seems they are a western european Jawa. Jawas are great doing everything they say on the tin. It runs with little or no maintenance goes for ever on a gallon of fuel that is any fuel that evaporates meths etc.
Just bigger and heavier to make them a little better on the reliablity stakes. If I had known of the problems with the marque I would have never bought one.
8-)