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Discussion Starter #1
Today I learned the valuable lesson to never let anyone incompitent use your bike. I have an 09 kx250f that's been on about ten rides. After cleaning the caked on mud off, I started her for about two minutes because I was going to change the oil. As I pulled back into my garage, my brother shouts and the exhaust tube coming directly out of the engine block was glowing bright red. I immediately shut it off. I drain the oil, only to find out that of my .9 liter capacity was filled with about .5 liters of oil, extremely short. I filled her back up with almost a full liter and started her up. I also checked the coolant and it's topped off. Here is where I have some questions (if you can't tell me anything already)
I started the engine. 5 seconds later felt the exhaust pipe, steming directly from the engine block, and it was already too hot to touch. Is this normal?
Then, when inspecting the oil level window to figure out if I had put the right amount of oil in, I noticed it had turned a misty dirty brown color, and the oil level is not visible, even when tilting the bike either which way. 5 hours later I checked the window, and it was no longer that misty dirty brown color. I am stumped and scared!
Is it normal for an exhaust to get bright red? What does it mean?
Is there a blockage in my exhaust?
What is the brown dirty color in my oil window?
Will my engine sieze if I run it?


Any help is appreciated
 

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Navy Vet Search & Rescue
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Today I learned the valuable lesson to never let anyone incompitent use your bike.
It sounds like there's part of the story you're leaving out.

It's not normal for the exhaust to glow red/get that hot. I've seen my atv do that once, but I was running very high rpm under heavy load as I plowed my way through some thick brush for about 20 minutes so it wasn't under normal operating procedures that it happened. When the oil disappeared from the sight glass, was the engine running or off, and how long after you turned it off did you check? If you were checking with the engine running, it's normal not to see oil in the glass.
 

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Discussion Starter #3
Well, the part I left out had to do with this kid I know, I let him borrow my bike. He took it up in the hills after a week of heavy rain. When he came back, it looked like he had completely mud bogged it. I cleaned the air filter... Checked the radiator fluid.

I waited till after I shut the engine off to check the oil. Between right after, and two hours later it was still that dusty brown blurry look.

Thanks for replying!
 

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AZ's Official Mechanic
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It's not normal for the exhaust to glow red/get that hot.
guess youve never played w/ the new 250/450f's... the yz is known to do this in very short order when idleing and im betting the kx is the same.... if its just sitting there idling w/ no air flow then its gonna get very hot since these bikes are setup lean from factory..... is it all stock ? plus its a TITANIUM PIPE...
as for the oil... could be some of the old oil just sloshing around till it was mixed..... is it cold/cooler there ? could be some condensation in the window... calls for 1 liter from what i see on the web.... as for oil level.. bike straight up and down,, level and cool/cold then check it... fill it to the correct level in window....
oh and run high test gas in this thing at all times... got some serious compression in this little beast... :biggrin:
 

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Discussion Starter #7
There MAY have been some dirt/water sucked in through the air filter, because when i cleaned it it was really dirty

but since I changed the oil, what could cause that brand new batch of oil to turn brown already? Wouldn't changing the oil remove most dirt and all waterfrom the engine? Still, why is my exhaust heating so extremely quickly?
 

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Discussion Starter #8
Yes It is all stock. It was ideling for just two minutes... I've never known forit to get this hot this fast.

It's not too cold here, around 60-70. It's not condensation... It only happens after I start it and stays there for severL hours. Rite now I can look in the window and see oil
 

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guess youve never played w/ the new 250/450f's...
You would be correct with that guess but I would be surprised if even those bikes would get to a glowing red status as quickly as he's describing.

If you get water into the oil it can take multiple changes to get it all out. If you know it's got water in, it's usually best to just throw some cheap oil in the first time and run it for a few minutes then drain and replace it with new oil of what ever brand/flavor you run in it.
 

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Discussion Starter #10
I am afraid to run it bc the amount of time it takes to heat up! I don't want to sieze, or make things worse.

My main concern comes from the pipe, how does it get so hot so fast!?
 

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AZ's Official Mechanic
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You would be correct with that guess but I would be surprised if even those bikes would get to a glowing red status as quickly as he's describing..
The ignition temperature for paper is reported to be 450 oC (842 oF), and the flash point of paper is estimated to be 350 oC (662 oF). The reference for all of this information is the Handbook of Physical and Mechanical Testing of Paper and Paperboard Volume 2; Edited by Richard Mark.

600-800+* for 2 minutes w/ no air movement and a thin wall ti pipe... gonna get hot awful quick.... esp since its not cold there....
pull the plug. whats it look like ???
yz's (and im betting kx's and crf's) get red very very quick... esp when you run them in cold weather and lean the system out even a bit more..... google it.. its been that way since the yz400f's came out back in 99 (?)
 

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Discussion Starter #12
Good info, I'm liking it. I just have a few more questions.

Do you think because my oil level was low when I drained it, do you think it may have caused engine damage? I don't know how long it was ridden like that, but it was only one ride since I had checked it. Should I start her up and see if she gets red again? I have a new oil change

thanks again!
 

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iv run into this on my moddied yz 80 i washed the bike off from mud and accidently got water into the muffler packing which had mud mix in it also and it restricted the flow of air out and caused my header pipe to glow red quickly. so i took the muffler apart cleaned it and repacked it and life was good again,just thought id share that info with you,might want to make sure you have flow out, push come to shove start it up and see it turns red again,if so take the muffler off and see if the header pipe glows red.if it still does then your machine is running way lean on fuel and may need to clean the carb out,any dirt that may have gotten through the carb may be blockin up the jet.or you have a vent hose glogged up or it may have inhaled crud through the vent hoses.
 

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it could have knocked a few hours off its life but nothing you can do now but make sure its full/clean and just ride it.. .keep an eye on the oil and make sure it doesnt get worse color wise...
until you fatten it up at idle its gonna glow red...if ya let it idle or ride it in cold weather...... do a google search and im sure you can find lots of info... the YZ's are known for it and the kx's are pretty much the same type 4-stroke (just have kaw on the tank)
 

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Discussion Starter #15
Good info guys, Ty
I have decided to take apart the exhaust and check/ clean it. I don't believe anything got in there but heck what do I know? If it continues I will take it to a buddy of mine and he'll figure it out. But it still hasn't cost me money yet and I hope it won't.
Thanks again, I will update when I get it all done. :)
 

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Good info guys, Ty
I have decided to take apart the exhaust and check/ clean it. I don't believe anything got in there but heck what do I know? If it continues I will take it to a buddy of mine and he'll figure it out. But it still hasn't cost me money yet and I hope it won't.
Thanks again, I will update when I get it all done. :)
Yes do check the exhaust pipe for water and/or dried mud laying inside the pipe restrckting flow. Be sure to drain your oil and change it two or three times if you find water in the crankcase and/or oil. You can stand the bike up against a wall to see if water drains out of the pipe.
 

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Discussion Starter #18
If it's 110% normal for a yz... Why hasn't anyone seen it firsthand on a kx? Just inquiring. because if it's not COMPLETELY normal, then something had to cause it

Ty zoro. I'm begining to think I was just freakin out when I saw the pipe bright red, but that is extremely unnatural to me.

One more question:
upon starting my bike (or any newer model 4stroke) , does the exhaust get too hot to the touch in <10 seconds? Because that's what mine did when trying to run it again, and it scared me. If it's normal, I'll have the courage to start it and run it for several minutes to see if the exhaust gets red hot again, without fear of seizure

thanks again guys! Lots of good info :)
 

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I did a quick search on Google for "KX250F pipe glowing" and it returned almost 8,000 results, so it does appear to be common.

Titanium does not transfer heat very well, so the pipe near the head will be much hotter than the pipe 12" away.

Isn't the KX250F liquid cooled? If so, then the coolant temp is what you need to be concerned with, not the exhaust pipe temp.
 
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