Eddy_t
ArboristSite Operative
What nmurph said. What you see in the picture tells you almost nothing.
OTOH, if the insulator, after some full-load running, is white to light beige, with a dark band next to the metal plug body, the plug is fine, for the existing engine conditions and mode of operation.
If the plug is clean & white all the way to the body, the plug is too hot. Had this happen recently with a PP4218. Went a step colder with a reputable plug (NGK). Maybe needs still colder. This is more about the plug than other stuff. A fouled plug is cheap. A molten piston crown, not.
If you adjust carb by a tach, then IMHO you're the same sort of idiots that felt compelled to totally bugger the adjustment of the carb on my 40 cc RedMax.
A tach is a good way to tune a tool, it also gives you an idea of what to listen for, I use plug colour to check if I do tune by ear, but I prefer a tach when pushing the tool to its max rpm