I've got a 2001 YZ426f which I recently installed new piston and rings along with new valves, guides, seals, etc. I also had a blueprint port job done to the head. Now when riding, I am fouling a plug every ride. The carb has the stock jets. My spark plug is black and sooty when I check the condition. Any suggestions on how to adjust my jetting? It seems to bog a little at 1/4 throttle. I know my Pilot jet is #42. Is it running rich and should I go down one size on the pilot jet? Any suggestions would be greatly appreciated.