Pete thanks for your input and offer. I will take you up on it if what I have planned is unsuccessful. I should have the new gaskets in hand by Saturday. They appear to be both thicker and larger in diameter. I ordered several, just in case. The leak is at the top of the gasket which makes sense when one thinks of assembly with the ring inserted first, it settles at the lowest point leaving only a narrow contact patch at the top. A larger diameter would be very good to offset this, as would a thin spacer inserted at the base of the gasket to help center while tightening. If the gaskets ordered are not substantially thicker I plan on double stacking the gaskets, which would probably "blow out" in short order but hold long enough to verify the leak as the main or only problem. Not having extra gaskets prevented me trying this earlier. Reuse of a damaged gasket was not a permanent fix, but did show a short improvement in the problem. At any rate I'll not adjust or change out any other components until I have a good seal at the exhaust. Chasing a problem with multiple solutions before eliminating an obvious one is a sure fire way to frustrate a happy outcome. One extra thing I noticed when checking for spark before initial startup was that the intensity and color seemed a bit weak. It was during the day so I plan on checking this out as well in more subdued lighting conditions after fixing the leak...original Chinese plug so an NGK replacement is in hand.
Again Pete I thank you for the very kind offer. I'll keep you informed. Rick C.