7. What is the recommended spark plug for the Atomic 4?

The original factory recommendation was the Champion J8. However, we prefer the Champion RJ12C. We would point out, however, that there are quite a few plugs that are reported to work very well in the Atomic 4, so if you have a particular brand of plug that is working well for you, there is no need to rush out and change plugs.

By way of background, the main difference between the J8 and the RJ12C is that the J12 represents the next higher heat range from the J8, and this increased heat range seems to help the plugs to run a bit cleaner in most of our engines. Some years ago, Champion left numbers 9, 10, and 11 out of their numbering system, but when we checked with the factory, we were informed that the increase in heat range between the J8 and the J12 was a modest one. They explained further that the operating temperature of a particular plug is increased primarily by simply thinning out the porcelain around the center electrode. Their explanation seems to make sense, since you don't see a lot of difference when you look at the center electrodes of the two plugs.

The “R” designation means that the plug has internal resistance, which is very beneficial in preventing interference with electronic equipment as well as providing a slightly stronger spark.

The “C” designation means that the electrodes are made of copper. - Updated: November 4, 2003