Lawnmower Engine (Should the spark plug hole expel a black residue?)

Been working on a small lawnmower engine.
Put away working, it is now the middle of winter. Normally very easy to start, got it to run once a few days ago (very hard start) then never since. It will not even try, no chugging.

One of the few remaining mysteries, even when dry the spark plug hole expels black residue when the engine is cranked. Is this normal soot residue, or a concern?

I have replaced the gas and oil. The air filter is very clean.