Bike in question 79 XR 500 So my plug turns black quickly with carbon. That means it's running rich doesn't it? Could an incorrect float level be the problem or would it be in the screw settings? The plug looks black and dry when they stop working after only maybe 1 or 2 hrs not sure on the time but they don't last long. Other than that the bike runs great and has lots of power. Oh black exhaust to when revved. Can someone point me in the right direction to resolve the problem?