The Bike: 01 WR426F, PowerNow, P-38 Lightning, Gray Wire Clipped, K/N Air Filter. The Problem: Put in a fresh plug and the bike will run fine until I stop for for a long break like lunch. When I restart it will stumble and backfire for a couple miles then run fine until the next long break. Pulling the plug at this point shows light gray. On the second day when first started it will stumble and backfire for the first couple miles and then run great, after a while the plug will foul out and the bike will quit running. Pulling the plug at this point shows black. It will not start again until I replace the plug. I have jetted, moved the clip position, changed brands of gas and adjusted the pilot screw but have not been able to eliminate his problem. Adding the PowerNow and the P-38 seemed to shorten the overall span of time the plug would last before it fouled fout completly. Getting pretty frustrated, any suggestions?