The Killer Bee was made at the request of the Free Flight community to meet the needs of Nostalgia FF flyers. It had a special, high strength, better balanced crankshaft, a washer behind the drive plate to allow use of electric starters, big bore venturi and a special cylinder. We were not allowed by NFFS to use the high compression head, because it would then outrun and outlast the Holland Hornet.
The final ones C*X made were just the product engine with a colored backplate.
The "real" ones had the yellow plastic needle valve extension and anodized crankcase as shown in the photo in an earlier posting. Accept no substitutes or you are being ripped off.