It is completely normal for our headers to turn a bright red color when you first install and run your new FMF Racing header. This is a standard break in period that normally takes about 20 to 40 minutes. If the glowing persists after this break in period, it is recommended to check your jetting as it is possible your carburetor is too lean. If you are unable to properly jet your machine, contact a local certified technician to look at your carburetor.