RE: Webra .50 Speed
Tom,
It seems you ran this Webra way too rich...
It only needs ~500 RPM below the absolute peak to keep it a bit cooler, but during your runs it was mostly four-cycling and much slower...
I saw such an engine exactly, peel its sleeve while being run like that (or even somewhat richer).
...The only non-OS I have ever seen peel its nickel...
Letting an AB(X) engine run too cool during break-in, is akin to letting a heroin junky get his fix... It will never do the engine any good...