Glowing Headpipe! Help!

6 replies to this topic
  • Brad_Brown

Posted May 18, 2000 - 03:37 PM


I just put my stock head pipe and silencer (minus the baffle) back on my bike to do some trail ridding. The only change from stock I have made is a 172 main jet and I have changed to the YZ timing. I just cranked the bike up and let it warm up and the head pipe is GLOWING red hot! It starts at the head then starts moving down the pipe! PLEASE can anyone help? Is this normal? I think the pipe is bolted up correctly. Thanks, Brad

  • tom13

Posted May 18, 2000 - 05:18 PM


I did the same thing and had the same thing happen. Look in the archives or the tech section and they have a list of people on this list and the jetting they are using with their location. I just looked at some that were in the same area/elevation as me and used thier settings. Now my bike doesn't glow anymore. Hope this gets you going in the right direction(I changed my main, pilot and needle).

  • Brad_Brown

Posted May 18, 2000 - 05:35 PM


Tom, Sorry but I put the wrong email address for me before (if you tried to email me). My correct email is:

Was your bike too lean? I don't think I was having any problems before today (I have never really looked closely at the head pipe but I have to believe I would have seen it before if it were glowing). Was you bike too rich or too lean? My guess is a lean conditon would cause the bike to run hot. But I went up on my main jet and haven't changed anything else. I did give the bike a really good cleaning today too. Could I have knocked something off the carb? Disconnected something from the carb? I am really baffeled here!

Thanks for your help, Brad

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  • Matt_Porritt

Posted May 19, 2000 - 12:56 AM


Headpipe glowing is normal.
When you remove the header and feel how light (and thin) it is, you'll realise why it glows.
After market headers don't seem to glow.

**Ride it like you Stole it!**
Matt Porritt
99 YZ400F
Rubber Chicken Racing

  • sbohanon

Posted May 19, 2000 - 02:35 AM


you are running to lean on the pilot jet. removing the baffle, air box lid and going to yz timing allows the motor to breathe easier. my yz4 did the same when new, i went to a #50 pilot jet and that took care of it. the larger pilot also eliminated to deceleration popping. also, other posts by clark suggests going to the yz needle.
i'm at 0-1500 foot elevation, so your jetting my differ.
ps, before changing the jetting, check the hot start circuit and make sure its not partially open or leaking since you did a good cleaning and may have altered something.

[This message has been edited by sbohanon (edited 05-19-2000).]

  • Clark_Mason

Posted May 19, 2000 - 05:48 AM


With the YZ timing I would go to at least a 48PJ, and a main jet range of 178 to 182 for altitudes below 6000'. I believe you are runing lean.

That said if you run the bike at idle for any lenght of time with the stock header at night and look at it it will glow. Running lean makes it worse.


  • Dan_Lorenze

Posted May 19, 2000 - 05:58 AM


Brad, I would agree with Matt, This is normal and has happend to me when my bike gets real hot. My jetting is stock and crisp. The motor runs hot! Dan


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