Be careful trying to jet the carburetor by "reading" the spark plug.  I have many 55 drums full of burned pistons that customers said that the spark plug indicated their jetting as safe.  Cold weather requires the jet sizes to be increased not reduced in size.

How does one tell if the jetting is correct if not by the plug? Needing bigger jets in the winter is something you learn pretty quick in Michigan. I'm spraying premix all over and mu plug is black and everything past half throttle is just bad (sputtering like its loading up). All these signs made me think the jet size needed to come down. 260 did the same still but it was a lot better.