When the engine warms up and sits during plug cleaning the engine heat
drys out the water in the magneto and/or the plug wire. Result is the
problem is gone. I would test the spark plug with a pressure test to
make sure it is not internally cracked and will fire under pressure
and I would also high voltage test the plug wire or just replace that
wire. Also inspect the distrubitor in the mag for carbon tracks.

Thanks, John. My A&P and I are going to check all that out
tomorrow.

Incidentally, I've noticed a wide variation in pricing on new spark
plug wiring, ranging from ~$170 to $300. This is a HUGE variation,
for something so mundane -- can anyone comment on why this is?

My A&P is partial to the Unison ("Slick") brand, which is over $300.
He says they are more expensive because each piece can be easily
individually replaced, whereas the cheaper brands just "crimp"
everything together, making them harder to repair.

Can anyone recommend (or steer me away from) a brand?
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"