Originally Posted by Kevlarr
Guess you haven't heard the old saying, "Pistons, the breakfast of Champions!"
Yep, I have a John Deere tractor that uses the Champion 71 (RC12YC) plug and I switched over to the Autolite 3924. I like to get out the DMM/DVOM/Ohm meter and check plug resistance. The Champion 71 measured in at 15.1K and the Autolite 3924 measured in at 4.82K, so I use the Autolite. Too much resistance can fry the ignition coil.