From Neil (who also made the incredible Rollerball Action Figure)...
Hey there, I saw on your blog you were interested in fat wheeled bikes.
I had a Yamaha BW200 until last year, when I sold it to a mate who still has it.
They were made in the mid 1980s, off road only, with a 200cc engine and then later with a 350cc.
If you look on my blog manisatthewindow.blogspot.com, the very first picture posted is that bike. (Won't take long to find, I haven't posted that much).
They are pretty rare in the UK, mine was the only one I ever saw.