jc whitney pipes. 155 mains 45 pilots. k/n pods. I put new plugs in it and ran it for about 15 minutes. I took the plugs out and the center electrode, insulator, and ground strap are white. I'm assuming this means it is running a bit lean. i have the air mixture screw set at 2 1/4 turns out. Any guess at where i should start with that screw?