It is a Honda S90. A kid at school my high school had a shiny new one; that was about 1970. In the early '80's the Thai government provided me with one for work. It was ok for my needs (70% on unsealed road), and ok on it's day. However, already over 12 years old and much abused, it was no longer very reliable.Pretty sure this in not a 250 but the dealership that I just bought my CBR from is a collector of vintage bikes and has some nice old Honda's throughout the showroom.
We had a small conversation questioning why Honda has not come out with a 'new' cafe racer retro. Not sure about the CB400, but I think Honda could sell a lot of something like a Tu250.