Your .061 was designed by Clarence Lee even before K&B owned the design. Yours is an early example with the perry carb. They later had some with an irvine carb then the K&B Block carb then the finned carb as on your .40 then the finned with remote needle. The current incarnation of this engine is still in production although probably not for long. It was announced that the twister will be discontinued and a new conventional head ABC .61 will be introduced.
These engines are very powerful for and engine in the .40-.46 weight class. Their power is very low for the .60 size class but since they are light and run so reliably they have been well accepted for a long time.

By the way: This engine also was involved in a crash or similar event as the muffler should bolt on not strap on.