So I was having 4 stroking issues at low rpm's and my motor was feeling sluggish. I am at 5,000 ft above sea level and using opti 2 at 100:1. I was running an nt carb with a .60 jet, and the needle set at the top (leanest) and these were my issues. My plug would always be black, with these settings. But then I tried something else. I got an NT speed carb and an HD lightning CDI. WOW For the speed carb, I put the same jet (.60) literally the same one as the nt, and did the same needle setting. I am not lying, the motor felt so good, there was no more 4 stroking and she just felt strong, and for once I was really enjoying the ride. Put in a new plug, and went on a 4 mile ride (which in my past experience is enough to get some color on the plug). I was going half-3/4 throttle most of the time, and at the end of the ride I rode about 10 secs WOT and then shut it down without letting her idle. Plug=white. not even the smallest trace of oil on this plug. Now I am going to do some jetting changes tomorrow, I am just looking for why this would happen with the same settings as the nt carb? Just curious and want to learn. Thank you!