Here's another pic showing the "cloneness" of the Royal 46 alongside the OS46SF.

I've also posted a pic of the Royal 45, it comes with a little story to tell. I purchased the 45 second hand & when I ran it, its performance was extremely disappointing with its max RPM about 3,000 less than my OS46SF using the same prop, plug & fuel. I pulled the engine apart & to my amazement found an internal "modification" performed by the previous owner. One of the transfer ports (the one immediately behind the "Royal 45" badge casting) has been blocked off with one of those hard setting metal type epoxy fillers. After approx. 45 minutes of careful scraping, I had removed all of the filler. Re-assembled the engine, fired it up it & its performance then zoomed to be on par with the 46SF (actually 200 RPM less) [8D]