Cub spark plug threads for compression gauge?

Sat Dec 25, 2004 6:21 pm

What's the thread size of a Cub spark plug?

I want to get a compression gauge and need to make sure it has an adapter that will fit a Cub.

Thanks,
Dan

Sat Dec 25, 2004 6:32 pm

18MM. Most testers should work with it.

Sun Dec 26, 2004 12:01 am

If you have an old engine (not a Cub) with a big obsolete sized sparkplug, most modern compression testers will not fit the hole. You can make a reducer by removing the porcelain insulator and center wire out of an old plug. It's a bit of work to break the guts out of a sparkplug! Once you have only the threaded metal shell left, screw it into the plug hole and you can then use a hand-held friction fit compression gauge.