On Thu, 6 Dec 2007 16:08:18 +0000 (UTC), Meat Plow
wrote:

Under compression whatever contaminants that are fouling the plug get
pressed against the insulator and plug tip making a pathway for the spark
to ground instead of across the tip. Having raced 2 stroke dirt bikes back
in my 20's I've seen this many times. Anyway that's my theory FWIW.

I read too much into _failing under compression_.

I have experienced a bad plug right out of the box...before pre-gapped
plugs. There was no time for fouling as the plug was new. It had to be
replaced immediately after install.

I prefer fouled plug term over failing. Just me