Spark plug threads


Old 08-10-06, 06:12 PM
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Join Date: Jul 2003
Location: Montevallo, Alabama
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Spark plug threads

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.
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Old 08-10-06, 07:59 PM
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Most auto parts stores sell spark plug thread chasers. If they aren't too bad, it should work well. Especially since I doubt your compression guage has nearly as many threads as the spark plug has. The plug can reach down farther to get the threads untouched by the guage. I believe it's a 14mm, but I can't swear to it. It's a common size and most plugs have the same threads. Some old flathead engines had larger plugs, and some motorcycles have smaller plugs.

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