Fouled Plug and Red Hot Pipe

Hey I just got this new 2001 the other day. Only rode it 4 times and the 5th time it didn't start. Fouled the plug. It was only like 40 degrees today and wanted to ride. I got it going again with another plug and before I stuck everything back together I saw that the head pipe was glowing red about 2" from the head, right below the radiator. Is this normal? Only ran it with the gas from the float bowl. I'm an auto tech and what I've found that causes that on cars is late timing and too much fuel. You guys got any idea's. Haven't even run 5 gallons of gas through it yet. But love every minute of it.

The glowing pipe is normal, especially if not in sunlight. If it glows real fast it is probably too lean, since you were idling, on the pilot. Leaner is hotter EGT. But don't panic, glowing pipes are normal.

The fouling is most likely due to starting technique, especially if last bike was a two stroke. It could also be starting and not letting warm up before killing it, running with choke on too long etc. But most likely problem is twisting the throttle intentionally to prime it with AP (like pumping pedal on a carb car) or accidentally from two stroke habit. Don't prime much if any, even if it doesn't foul mine, the plug will be wet and I will have to blow it off with compressed air if I 'prime' it. Putting right hand on front brake master cylinder will cure the twisting while kicking problem.

good luck,


The headpipe on my 00 426 has never glowed red before, but I have seen it on a few XR 400's. I wouldn't worry about it. Mark is right about the fouled plug, don't goose the blue beast when you try to start it. What I have found that works good is just pulling the front brake lever when you're trying to start it. It will keep you from twisting the throttle, and also keep the bike from rolling forward (which can be awkward sometimes, especially when you're trying to learn to start a 426). Get your starting technique down, and you probably won't foul any more plugs. Is your bike brand new or used? If it is used, pull the carb, check the jetting, and see if anything is plugged in there. Someone may have jetted it wrong, and this could cause the glowing headpipe.

The pipe on my '01 glows red almost seconds after it starts (I've never started it in 40 degree weather though, bbrrrr...). Sometimes you can save the plugs by cleaning them with carb cleaner. Ditto what they say about the fouling, I wouldn't sweat it until you're fouling them a lot or you know what series of events causes it.

Thanks guys. I see that it has a nuetral switch, which may keep the timing later when it's not in gear and reved up. Any idea's on that causing the hot pipe???????

How fussy is the tps also?????? Anybody know the affects of being to high or low????? These things can cause all kinds of problems with cars, like no starts,etc.

As for the throttle, I don't believe I twisted it. But I have it in my shop and people look at it. Oh,new bike and what's the first thing you do. Twist the trottle, right. This maybe what happened maybe. I couldn't get the other plug cleaned up with out sandblasting it and that didn't work very good. Would miss fire at times and then fouled again. It would really suck to drive 200 miles to a race and not get it started.

Thanks again

The head pipe on the this machine is quite thin- walled and the red glow is the result. Lots and lots of guys have been concerned about this.

You can easily drain the float bowl to prvent people from quirting fuel into the cylinder while it sits on display.

The TPS is tied into the ignition map. Don't touch it, or, set it to factory specs via the manual. My opinion only.

If you drain the float bowl then I'm pretty sure that there is still some gas in the accelerator pump until it all gets pumped out, so someone can still flood it by twisting the grip.

As Boit said I wouldn't fiddle with the TPS. The manual says not to mess with it.

Everybody should know, but all the head pipes on most 4 strokes glow. I had a small block chevy that would light up the drive way when I rolled in after work every night. Its usually just not dark enough out to notice it. Personally I think its bitchen! Pipe glowing all red hot and flames blowing out the end, dirtclods flyin all over, spectators diving for cover from the roost .......and the noise, the beautiful noise.......

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