Back in the early 80's used to do a bit of trail riding with some blokes from work. The father of one one of the blokes (he was 47, so old to be riding dirt bikes i thought!!!) turned up with this weird 250 Kawasaki MX bike that he'd apparently bought from a used car yard. Non of us really knew what model it was, had a green plastic tank, an underslung chamber which swept up at the back with a sort of cone shaped silencer which flaired outward at the back and went like the clappers. The outer cases were sand cast, which I thought was unusual. After a few reliable years it was eventully sold off to a young relative of his. As I was getting interested in VMX in the early 90's I tried to track it down only to be told it had been trashed. I've yet to see another like it, but I'm guessing it must have been an F11M.