wr400 red hot header

I just bought a '99 wr400. The guy changed over to the YZ cam timing, put an FMF header on it, and supposedly had it jetted at his local shop for this setup. At idle, the header turns faintly red hot. Also, I get a major hesitation if I gun it at low rpm. This tells me it's jetted too lean - but I'm new to the bike and could be wrong. BTW, it runs great above idle and starts easy. Can anyone provide a pointer or two? I don't want to ride it with a red hot header. Thanks.

Its cool dude...it is normal at least with the stock pipe and I can't believe the FMF would be any different. I freaked the first time I saw it at night too. Makes you uneasy eh!

how long do you have to warm it up before it starts glowing?

I want to see this for myself

As far as the red header at idle goes, I think that it is normal. Mine is the stock pipe with the shroud broken off and it glows orange at idle also. Check the many jetting posts through the search mode to help with your carb.

The pipe glows before the bike is even fully warm... probably takes a minute or two. The exhaust temp must be really high and/or the header is abnormally thin. I've now heard this is normal from everyone I've asked - still gives me the creeps!

Thanks for the feedback. Anyone else experiencing the glowing header on their 400/426? I need a few more yes's before I feel OK about it...

Mine glows red you can see it better at night

My WR250 with the stock header dose the same thing. My brother in-law has the WE426 and it does the same thing. I think they all do it. I do not wait long enough to see it glow, I get on it and ride like hell.


I was similarly concerned when I first saw my header glowing red at night. It usually takes around a minute at idle for the pipe to glow orange.

A quick search on TT laid my fears at rest :)

yes it does.

Definitely does.

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