I went out and changed my oil and cleaned the filter today and when I started my bike I let it run for a couple of minutes and noticed the headpipe got red from the head to about 3 inches out. I have only had this bike (98 yz400f) for about a month and have never noticed the pipe getting red. I did just put a new White Bros. R4 silencer on last week and rode it for about 30 minutes and didnt notice the pipe getting red, the bike runs fine. I have raced the bike 2 weeks ago with no problems also. but today is the first time I have ever had it running in the dark, all my time on the bike has been daylight.

Thanks Skip

It's normal.

That's normal, nothing to worry about. :)

That is completely normal, although... you want to make sure not to keep it idling for too long. Because in a liquid cooled engine, air flowing into the radiators is what cools the engine. When you are at low RPM and idling then no air is cooling the fluid, and the fluid isnt being circulated very fast.

Also, the reason you never see the headpipe get hot while riding is the air is cooling down the headpipe. Even during the daytime though, you will see the headpipe get hot if it idles for too long.

The first time I saw the red headpipe, I thought it was very impressive... :)

Thanks everyone for the help, This is an awesome site and I hope it helps all you guys as much as it does me.

Thanks again, Skip

Oh, and be careful to keep any "meltable" pants away from the header... I melted about a 3by3 inch hole in my wind pants without knowing it. Then, when i went to wipe the goop off the header with a rag, the rag caught on fire, lol. So just make sure you are careful :)

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