Header pipe glowing red

I've seen quite a few posts on this. Any big 4 stroke will do this if the pilot jet is plugged, right? It's a severe lean issue. My ATK did it once. The pipe turned cherry red after a few minutes idling, you could almost see throught the header. I took the carb apart and the pilot jet was completely plugged, cleaned it and problem has never resurfaced. This is an air cooled 604cc rotax and when the pilot is not plugged you can idle for way longer than makes sense and the header will not change color. Should'nt a H2O pumper run cooler? I bet Yamaha jetted these things lean for emissions.

Just a common occurance while idleing in low light for a extended time. Just don't idle long, go ride. Mine has done this with different pilot jetting. :)

I can't seem to tune this problem out of mine so I just don't let it idol long. Let me know if you get it worked out.


I have brand new out of the box '02 WR426F Canada model. Without modification, header glows red. I am definately following Jeckel advice. I will not idle it long until I figure on a re jetting configuration. I am looking for a jetting plot for 4000 ft., general use ( trail and track ) leaning towards torque rather than horsepower. The bike is good now in this respect ( stock form ) but stock is no good for a bike of this caliber.


There has never been a correlation between the glowing headpipe on these bikes and mechanical issues. I would be willing to bet that you could make any jetting change you want and you would still see the glow as long as the bike idles and doesnt move.

I could be wrong, I will admit, but, I don't think anyone on this board found any mecanical issues that changed the condition. This could be a characteristic of the head pipe and have nothing to do with how the bike is setup.

Just my opinion. I didn't think mine did this until I actually started it at dusk the other day.


Every Yamaha 4 stroke I have owned has done this. I have a DR400 that gets bright orange when it idles.

I just look down and hope that when I crash that pipe never gets near me.

Back in the day a Maico crashed into me and I ended up having the cylinder burn my butt. I had burn marks that looked exactly like a Maico cylinder.


Not meant as a flame just information but I have stated it before but with my current jetting setup the header never glows red, doesnt matter how long I idle it. The header glowing red is a direct result of a bike set too lean at idle. I live at 1500ft and the temp these days is in the 60's

have you ever started it at night? and let it run for a couple of minutes? I ask because I never noticed that it glowed, and figured it didn't, until the other night when I started it in the dark and noticed the glow as I shut off the garage light.

I have started mine at night and if there is any glow ( I wouldnt even call it a glow) it is not noticeable. I have started mine and let it idle for a while, just to see if the header ever got hot enough to glow and it does not.

Maybe theres something to what you say then.....

The pilot you are running seems really rich. I would not be able to get any performance out of my scoot going that rich on the pilot


or maybe the bike is still totally stock with the baffle and throttle stop still in. That way it can not get hot at all. LOL. Just poking fun. There are about 8 yz/wr's in our group. They all glow. I doubt it has much to do with jetting. I just think it is the hi revs and that our bikes are fire breathing machines worthy of a glowing head pipe. MUAHAHAHAHA.

My setup works for me and the type of riding I do which is mostly hill and trail. I do have the throttle stop cut and most mods posted here as well and have modified the stock baffle but have not taken it out completely, we have a 93 dec sound level to contend with here on the dunes, I am curently looking for a quiet muffler that wont rob power.

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now