I know that the larger YS engines have superchargers, but I am unfamiliar with the YS 63.

As YS puts it "Crankcase supercharging system unique to YS 4 stroke engines" which leads me to believe that they all do.

If it does the YS 63 would be far more powerful than his O.S. 70, and other threads I found seem to bear this out.

Apparently he may already have the O.S. 70.