Sorry to bring up this subject again but I have a 99 wr400 and the spark plug is showing white on the very tip and black around the outside, the ceramic part of the plug in the center is still white, there is no colour on it at all. I am running a dvp #4 175 main and 2 turns out on the screw. I have tried a 178 main but this only made the outer part of the plug even blacker. I have adjusted the screw but this didn't get rid of the white tip.I am running a FMF megamax 11 exhaust with yz timing air box lid removed twin air filter with shell optimax fuel which is slightly higher octane than premium unleaded.The bike runs nice and crisp right through the entire range.I have notice the muffler gets very hot but the radiator has never boiled or overheated. Is it normal for the muffler to get that hot that if you spit on it, it will sizzle? Does it sound like it could be the needle that is making the plug white and will putting the clip on #5 make it better or cause other problems? Or should i just leave it.I live in Australia and it about 16°c ambient because we are just coming out of winter and I ride about 0- 1000 meters above sea level.I have checked for air leaks and my hot start switch and they are o.k. I have read other articles on this site about people that have had the same problem but I coundn't find out what they did to rectify this problem . If anyone can help it would be appreciated.