what size jet did you have,,,,and which size did you buy?

 

Don't let this be a concern or use it as a tool to jet your 400ex. This is normal. Do a search on this sight and you will find that this has been talked about before. Mine did that stock and still does that with a CT Racing pipe, uni air filter , and a 162 main jet with the needle clip on the forth notch.

 

There are a number of ATVs on the market that the pipie will glow red, and be normal.
Yours is one of them. Good idea to change the jet in case it was a little restricted.
The glowing pipe on a lot of models is not noticed, as they have exhaust shields covering the pipe up.

----- Gimp -----

 

yea, the glowing red pipe is normal

DONT WORRY ABOUT IT

 

Funny that this question has been brought up...I posted the same question about one month ago. Like you, I have a hardly ridden 2003 400ex which is stock. I noticed the glowing pipe around dark also. Seems like you are getting a lot of the same responses that I got...lean carb. I talked with two different Honda mechanics, and they both stated that the glowing pipe is normal (one of the mechanics owned a 2001 400EX). Here is the best explanation I got....You are noticing that the pipe is glowing around dark or in the dark because the pipe is only one layer of metal thick. On the older models, not sure what exact years, but they contained two layers of metal around the exhaust pipe. Hence, without the second layer hiding the first, you are seeing a hotter pipe. If you are worried about lean or rich, clean your plug, then go and ride for a while....when you get done check the color...grey means lean, while a black plug means you are rich. Hope this helps.

 

Hmm... I've never noticed a 400 glowing at the header before, so I assumed he was running abnormally lean, causing more heat and.... you get the picture. Guess this seems to be the norm for this bike? Still to be safe, I would do a plug chop just to make sure!

 

To the best of my understanding, it is the norm to notice this at night or in dim conditions....it would not be normal in the middle of the day. Believe me, I would be the first person in line to have it fixed if I thought something was wrong. Further, neither dealer mechanic wanted me to bring it in...I pretty much would have had to beg them to look at it, which seemed strange to me. Most of the time a dealer mechanic will be more than happy to take your money. My vote is that its the norm since the muffler has only a single layer of metal for muffler...think about it...its getting pretty hot right there next to cylinder head....so yes, the first 10 inches of your muffler is going to be extremely hot as the gases are removed from the muffler system.