Honda 125 from the mid-to-late 1970s? Single or twin. Solid-enough bikes which won't cost a fortune in petrol.
Moving up in capacity a little - Honda CD 185 is one to avoid: I've never known a good one. Odd, because the CD 175K and both versions (6v/12v) of the CD 200 are generally well regarded, as is the rare CM 200T (custom). The CB 175 and CB 200 were good, but looking somewhat expensive for what they are these days.