breethit

Member
Nov 7, 2006
3
0
Hi I own an Yamaha xt 225 and we just rebuilt the top end, everything looks great, oil circulating well, piston and cylinder look good, spark plug not white but...when we run it for about five minutes, the exhaust header glows red. Is this normal? We don't know what's normal for this bike because we had to work on it right after we bought it. Its not the timing, and it sounds really strong. Its a four stroke and I'm DYING to ride it but an worried that it might damage it if it overheats. Any comments?
 

Okiewan

Admin
Dec 31, 1969
29,555
2,237
Texas
Don't know about the XT specifically, but all modern 4-stroke's pipes glow red. Bright red.
 

Octane250F

Uhhh...
Oct 21, 2006
174
0
The only time Ive seen a headpipe glow bright red is when the engine is running lean. I cant believe thats considered to be normal.
Its very possible that the bike is jetted for the summer and now that its getting colder its running lean and thats causing the headpipe to glow red.
Trying richening the pilot screw. If you have to turn it out more than 2 1/2 turns, you need a bigger pilot jet. You also might want to consider a bigger main jet too.
 

Octane250F

Uhhh...
Oct 21, 2006
174
0
That still doesnt seem right. There is no reason why a headpipe should glow red-hot like that.
 

junkjeeps

LIFETIME SPONSOR
Nov 24, 2001
671
0
Never seen it on a bike, but I have on a Briggs engine. It was unburned fuel passing into the exhaust pipe and burning there. It was a timing issue. Motor was timed exactly 180 degrees out. It ran, but after about 2 minutes the exhaust was glowing. I know you said the timing is correct, but could it be possible your 180 out? Does the bike rev out correctly?
 

Jamz

Member
Dec 14, 2005
36
0
My dad started up his bike wr400 one night to just run it. He had it running on choke and walked away for a second and the header pipe started glowing BRIGHT red. He shut it off and after it cooled down, he started it up again off choke and it did not do that...stayed normal color. That would have been a rich condition....excess gas burning in the pipe.
 

76GMC1500

Uhhh...
Oct 19, 2006
2,142
1
Double check to make sure you've got the cam gear timed properly. I have a tt225 as well and I assembled it with the cam gear 1 tooth off. The pipe didn't glow red, but the bike ran really weird. It would idle fine, hit a flat spot off idle, pull hard in the mid, flat spot again, and then pull hard on top. Yours might be a tooth off in the other direction.
 

breethit

Member
Nov 7, 2006
3
0
Thanks for all the help!!! Its a 98. The bike sounds, smells and runs really strong, and it revs fine, my buddy is the one working on it. I'll ask him if its possibly timed wrong. It seems to get the most mixed answers! It does actually take about five minutes for it to get that color, if that makes any difference, maybe the choke is on too long...
 
B

biglou

It's normal, and it's been happening for years, and there are about 1,000 threads to prove it...

btw-If your timing were off, you'd know. I suspect yours is fine.
 

breethit

Member
Nov 7, 2006
3
0
Woohoo

Ok, thanks, he thinks its ok too. I wonder if the composition of the exhaust has something to do with it. We are going to finish puttin that baby together because I am dying to ride it. Thanks again for the reassurance!
 

02yz426f

Member
Nov 15, 2006
319
0
I have a 2002 YZ426F and it only takes 1 minute for the pipe to become glowing hot cherry red. No matter how long I ride it, the color never goes away. Do I have a problem? I have talked to several mechanics and they think it is a lean condition in the engine that might be causing it harm. I know you say it is glowing hot red, but does it go away after awhile of riding for you or does it always stay that way? Some people told me about it turning red then changing colors to purple and other odd stuff. Please let me know, I just dont want to ruin a $3000 bike when I could have it looked at for $80.
 

Halfast816

Member
Mar 21, 2005
34
0
As far as the guy with the 426 goes leaness will appear in the 426 as popping on decelleration. You could try a 48 pilot jet as that is what I settled on when I raced that particular model. If it doesn't stumble off idle I suspect your jetting is ok. Any four stroke will glow after five minutes. No need to ever let it run that long without riding it. As for the valves At least once every twenty hours of ride time. Actual ride time not the amount of time you are at your riding area....big difference. I suggest getting an hour meter to keep maintainence intervals regular and repair bills minimal.
 


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