As I learn more about the mechanics of my bike and attempt to do some of the upkeep and repair myself, I expect to encounter many things which will require a true mechanic or shop for expertise or equipment. I pulled the plugs (original HD 612R) on my 2000 stock Fatboy with 4K on the odometer. The front plug was a nice tan color. The rear plug however had a black sooty appearance which I'm told indicates too rich a mixture. How can this be? Does the back cylinder get the lions share of fuel? The bike runs well, just a bit cold natured. Not knowing what to do I improvised by reversing the plugs. This should tell me if the plug is at fault or something else is going on. First question, how many miles at highway speed should it take to burn the black plug to a tan color if indeed the plug is the problem? After that, what would be a reasonable second step? Compression test? Hoping someone has the time to comment, I thank you in advance. Ishmael PS The only engine change from stock is a set of V & H Longshots, baffles in place.