Hi I own an Yamaha xt 225 and we just rebuilt the top end, everything looks great, oil circulating well, piston and cylinder look good, spark plug not white but...when we run it for about five minutes, the exhaust header glows red. Is this normal? We don't know what's normal for this bike because we had to work on it right after we bought it. Its not the timing, and it sounds really strong. Its a four stroke and I'm DYING to ride it but an worried that it might damage it if it overheats. Any comments?