I purchased your kit for my 2000 wr 400 and put in the suggested blue needle 3rd clip 170 main and 42 pilot. It ran worse than the 160 main and 3rd clip 0bdrs. so I went down to a 165 main and it runs amazing. The only problem i had was that I was at about 2200 feet and 65 degrees, no humidity, and rode trails with lots of hillclimbing for about 4hours. I just checked the plug today when i was converting to yz timing and it was white, but it was brand new ngk right before i went riding. The steel thread itself had a black look but the entire insulator was white. I really didn't think I was that lean. Could it be that the new fourstrokes take longer to get a new plug to read right. or am I really that lean( it ran amazing, i smoked 2 xr650's). I'm running removed airbox lid and removed baffle, with no gray wire and cut throttle stop. I'm going to step up to a 168 main. If it doesn't turn the plug a little tan. I just assume this fourstroke is different than the others. Would moving the clip to the 4th notch be a better idea than going to a 168? the 170 just didn't seem to pull as good as the 165 and it would bog when I would give it gas. Maybe I just need to do the accelerator pump mod. help I just don't want to burn up this motor.