What's up fellow thumpers. I have a question concerning a fouling problem that I've been dealing with since I purchased my bike almost 3 months ago. After many many jetting changes, both by myself, and then letting my local Yamaha shop "CO Powersports" giving it a whirle,I still am loading up and fouling plugs. I'm not fouling plugs nearly as bad as it was at first. The bike runs good, sometimes great. But non the less, I usually cannot go more than 2 rides on a plug. My backgound is mostly with a 2 stroke, and to me a black plug denoted a rich mixture. On my '01 426, I'm getting the very common sooty black plug, "Carbon Fouling" I guess is the proper term. Again, to me this seems that the bike it to rich. My jetting now is much leaner than how it came stock. Here is the twist. Last weekend I was riding above 14,000 feet here in Colorado. Except for just a very minor loss of power, which is to be expected, it ran awsome. As I dropped down in elevation I started to get a lot of popping, and if I needed to whack the throttle just a little, it would load the plug up. I have been told that the popping is a sign of to lean of a mixture. THE MILLION DOLLAR QUESTION.... WHY IS MY PLUG STILL BLACK AND CARBON COVERED IF MY MIXUTURE IS TO LEAN. Any help would be appriciated. Today, I am expecting a call back from the president of the shop here in Boulder, hopefully with some kind of answer as to how my problem is going to be fixed. Thanks a lot, Later!