This unit was acquired from the estate of the original owner, who acquired it in Japan and then for reasons unknown brought it back to the states, put it in his basement, covered with a sheet and there it sat until his passing. The result, this is a very low mile, all original example of one of the first, if not the first, of a four-stroke motorcycle utilizing a Kawasaki designed and manufactured engine. The third photo is a 150cc example that was sold in Japan, note the Kawasaki Aircraft trademark in the casing. This unit has all the requirements to run, though I've never started it as I didn't want fuel in it and I damn sure wasn't going to ride it. So far as I've been able to determine this is the only example of the RSY known to exist. I don't believe there is an earlier example of a 4-stroke engine produced by Kawasaki Aircraft in the US.