The 23.6cc is a rare find. Why not just start with the much more popular 25.4cc instead. Echo puts this engine in just about every garden tool and cocktail mixer they make these days. Whatever porting advantage the 25.4cc may not have is adequately made up by the added cc's.

I have an Echo 25.4cc converted to CH ignition, and it has the power of between G23 and G26 - just as I'd expect.