Does anyone know the tap size for a RC12YC Champion spark plug. Aren't most plugs the same thread size? The reason i'm asking, is that I got two Kohler Command CV14 and CV15 engines in today. I pulled the plugs out of both of them, to check compression. The plug hole is so far back in the head, I guess I partially stripped the threads, trying to get my compression guage back in. The only thing I know to do take a tap and try to chase the threads. Anyone have any better ideas. It's the first Kohler Command engines I've worked on.