Spark Plug

Personally I would consider slightly tweaking the air fuel mixture before changing plugs. My 2 cents
Not sure how I would be able to do that when I went down 2 sizes on the primary side of my rods and the engine surged so had to go back to base.
The picture does not show it but only the top 1/3 of the insulator is white while the rest is black. There are about 2 threads that are black too. Maybe I could get a better picture from the side if needed.