I have a 2001 YZ426F. I have the Thunder Alley pipe ( stock header ) . I live at about 1500 ft and its around 85-90 degrees here. I installed a 168 main and a 45 pilot. I installed the Factory R&D accelerator pump mod to my carb and changed the needle to one that the R&D guy told me to. I believe he said its only used in Canada ?? anyway . I put the clip at #3 position, like he told me to and 2 out on the pilot screw. It has a very bad miss at the very bottom of the throttle at all speeds ( steady throttle speeds ) . I cannot seems to cure it from this adjusting the pilot screw. So the be sure I checked the plug to see if maybe I had a bad plug and it was very black . Too rich , so I changed the pilot and the needle clip leaner and the miss is still there. So I thought too many changes at once , I put everything back the way it was stock except the main jet. I was gonna do one change at a time . It still misses at a steady pace at the very bottom of the throttle. It cant be the main jet becouse I am not running that hard. I pulled my carb apart about 10 times yesterday and I know its not dirty . I have hardly ridden this thing since Feb. when I bought it. Maybe 1 or 2 times a week and I dont race or ride hard. I'm a novice rider. I havent a clue of what this can be anybody out there have any Ideas? is there a jetting guru out there? I am too nervous to do the BK Mod as I dont quite get the Timing of the pump squirt. Thats why I went to the P-38 lighning mod. Supposed to do about the same. PLEASE BAIL ME OUT HERE!!!! I know someone here on the best damn website period can help me .