Oh, one other thing. I learned plug reading from a plug wizard that champion
used to send to the races--can't recall his name but he was a great guy and
really new plugs inside and out (literally). Some things he showed me are:
-- plugs should always be read at the base ring--the little circle of
insulation that you can see at the bottom of the insulator--as well as the
sides and tip. You need a good light and magnifier to properly read plugs.
-- There's no such thing as reading a plug without a clean chop--if you're
trying to figure out what's happenbing at full throttle then your chop has
to happen at full throttle after a pretty long load--up hill is best. Cut
the ignition with the throttle wide open and coast to a stop. Likewise any
other throttle position.
-- The second place you look is at the edge of the center electrode. If the
plug is too extended, the base insulator might look fine but the tip edge
will be rounded from melting. You also want to look at the center of the tip
electrode (assuming it's not a platinum tip where the wire is too thin to
see anything) for a clean little ring of splatter from the sparks. If it's
not there your coil polarity might be reversed (look inside the side
electrode) which can give you fits with a high compression engine--you may
get misses at full engine load since it takes more potential for the spark
to jump from the relatively dull side wire. Sharp edges enable sparks to
jump at lower voltage (read up on corona effect if you think that sounds
silly)
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