That's what I thought too (wet & black plug = rich).
I'm not sure how to adjust the carb for this. I haven't put a new air filter on it yet, but if I pull the air filter off, it still has the knock. And maybe I'm hearing something other than the piston. The knock seems to be louder if the back tire is on the ground and stationary (at idle speed) and less loud, but still very noticeable, when the ped is up on the stand and the wheel is allowed to turn when the engine is at idle speed. Does this sound like a clutch issue?
I advanced the timing as far as I could, it's a little better now but still seems a little late and the knock is still present. Not sure it's possible to do anything about it if the stater plates are adjusted all the way in the counterclock wise direction.
I'm going to ride it in a bit and I'll see how it does at full throttle, which is what got the discussion going in the first place.
Thanks again everyone.