Originally Posted by chasbmw
If your airhead is dual plugged, use a hotter running plug in the lower position, because the hotter running plug will help burn off the oil etc that tends to end up on the lower plug, so with NGKs I might use a '7' in the top and a '6' on the bottom.
I am running 6's top and bottom on my bike. I am curious to see how many miles it is going to take for that issue to show up. At 3000 miles top and bottom are burning identically.