Maxpower has a point I think-
See previous thread Bruce commented on about Outlaws glowing header. Same principle. I too have seen this on circle track cars many times too (glowing headers)... I even had a similar problem with a XR400 dirt bike that ended up being too rich & made the header glow at idle. I think Bruce made a similar post then b/c I was making the problem worse... doing the opposite. He was right. His explanation even applies to the simplest of motors on a single cylinder motor cycle engine.