Glowing red header pipe

[03rm250]

Hi guys.

Tryed starting my crf today for the first time in two weeks and it was a b*#ch to start and finially when i got it going after about 5mins of idling the header pipe was glowing red hot.

Surley this can't be right, Last time i rode the bike it was perfectly fine.

Bike is a 09 crf250r dune 100hrs.

Any help would be great.

Cheers Daniel

[bogan]

exhaust valve knackerd would be my guess.

edit, so check the compression to find out

[03rm250]

if i checked the clearences would i be able to tell??

[steve_t]

Not running lean?

[03rm250]

im not 100% sure lol, bike run mint as last time i rode it.
oh and also while trying to start it some of the time it would backfire real loud.



Not running lean?

[Crasherfromwayback]

if i checked the clearences would i be able to tell??

If exhaust valve is tight...it could cause the exhaust pipe to get pretty hot. It'll also burn the exhaust valve and fuck it in no time too. Do a com test as Bogan says...AND do the valve clearances.

[CHAPLIN]

If you leave the choke on for to long this will happen

[kevfromcoro]

If you leave the choke on for to long this will happen

does it... wouldnt of thought so....
mayebe you are right......
i know timing will do it.
interesting thread

[Crasherfromwayback]

If you leave the choke on for to long this will happen

I'm not so sure a rich mixture will heat the header pipe that badly that quicly.

[vifferman]

With the exhaust being really hot, and the backfiring, it sounds like it's really lean - possibly an air leak.

[03rm250]

right.. have checked the clearences if sitting on bike.

exhuast; left is .005. right is .005.
intake; left is .003 right is .004.

acording to this website
http://crfsonly.com/howto/crf250x/crf-valve-adjustment/crf250x-valve-adjustment.php

the exhaust should be .011 and intake should be .005.

would this be the cause, or do these seam ok

[pete376403]

The header pipe on my KLR will glow red hot if it's left on a fast idle for about ten minutes. Nothing wrong, it's just a combination of a bit of heat and the air injection system that puts fresh air in the exhaust port to burn any excess hydrocarbons in the exhaust gas. It's only making the pipe glow because there's no cooling airflow.

[03rm250]

hhmmm its got me stumped. im guna try start it tomorrow and see wot happens.
then if it still does it its off to the doc.

[merv]

Was this at night time outside? My WR glows at night but it looks normal in daylight.

[03rm250]

was the middle of the day


Was this at night time outside? My WR glows at night but it looks normal in daylight.

[Ocean1]

Was this at night time outside? My WR glows at night but it looks normal in daylight.

+1

My KLX did it, was really obvious in tight stuff at night. And you should see the Buell at low speeds at night...

[quickbuck]

right.. have checked the clearences if sitting on bike.

exhuast; left is .005. right is .005.
intake; left is .003 right is .004.

acording to this website
http://crfsonly.com/howto/crf250x/crf-valve-adjustment/crf250x-valve-adjustment.php

the exhaust should be .011 and intake should be .005.

would this be the cause, or do these seam ok

Well, as your EXH valves should be 0.011 then what is hapening is that they are actually warming up and staying open!
This means that fuel is being burnt in the headder pipe, making it glow......
As mentioned will stuff your EXH valves in no time.

If anything if you ride it hard then the clearence should be BIGGER than 0.011, not smaller.

[Sable]

Take it to someone who knows what they're actually doing. The internet can only do so much.

[Max Preload]

Well, as your EXH valves should be 0.011 then what is hapening is that they are actually warming up and staying open!
This means that fuel is being burnt in the headder pipe, making it glow......
As mentioned will stuff your EXH valves in no time.

If anything if you ride it hard then the clearence should be BIGGER than 0.011, not smaller.

What he said. And it's always better a little loose than a little tight (at least for valve clearances, anyway...).

[slofox]

With the exhaust being really hot, and the backfiring, it sounds like it's really lean - possibly an air leak.

wot 'e said...

[03rm250]

Right , rang the honda shop from were i got the bike from aparenlty they are ment to do that, but im not convinced as it is a hard to start.
its going into the shop on monday.

[CHAPLIN]

I'm not so sure a rich mixture will heat the header pipe that badly that quicly.

I left the choke on while I nipped back into the house to check something on my wr250, would have been about 1 1/2 minutes when I came back, the header was glowing red, flicked choke off and it stopped glowing.

[Crasherfromwayback]

I left the choke on while I nipped back into the house to check something on my wr250, would have been about 1 1/2 minutes when I came back, the header was glowing red, flicked choke off and it stopped glowing.

Yeah, but you'd probably find the same thing if you left it there on a fast idle without the choke on too mate. Don't think it's due to the rich mixture...as I first said...tight valve!

[scumdog]

Retarded timing will do it easily, check it.

[Grasshopperus]

I want to run red-hot exhaust pipes. Please find out what's the problem then tell us all how to emulate it. That is all.

[The Pink Panther]

:shit:Top end rebuild another MX 250 bites the dust . :shit:

[DesmoDAZ]

Here are a couple of thread replies from the aprilia forum about the glowing headers.

My sxv 5.5 does it when first started if run on 1/3 throttle for a while, if I blip the throttle and vary the reves it does it less, no real big issue at all, it doesnt do it at WOT.

Rich fueling dramatically reduced the combustion temp...resulting in very little pipe glowing. Liht throttle setting will allow more air to back flow in the exhaust and this does tend to light off unburned mixtture in pipes but still adding a richer fuel mix will about always result in lower exhaust gas temps and much less visible color in the pipes.

It is funny but true...pretty much all bikes will do this. I see it on the dyno every day but to differing degrees. I have even managed to get a two stroke expansion chamber this hot...the whole thing bright red and alive from header to stinger so yes, it is normal-ish.

This is the part about varying degrees. Under about 2% CO at light throttle is where the most color will be visible. Always on twins, the rear header looks to be glowing brighter (at least on the dyno and on the road) since it get far less air cooling being all shrouded in parts back there.

[blackdog]

wicked. that looks almost molten!