New FMF Exhaust for CRF250R Header turing Glowing RED almost instantly!!

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crf250rjcd5151

Member
Dec 19, 2007
15
0
New FMF Exhaust for CRF250R Header turing Glowing RED; Also finished install pics!!!!

Anybody have problems with this??? I put the FMF Factory 4.1 slip dual exhuast first, started it up sounded fine and ran fine with the stock header, but it lit up bright red almost instantly and shut it off.

I then bought the stainless steel FMF Powerbomb header and after that brutal instal(not quite any easy fit!!!) it is doing the same thing.

Anybody got a clue why???? The bike sounds like it is running fine but it seem to be getting really hot fast. Is there anything I could have done while installing to make this happen???

http://www.dirtrider.net/gallery/showimage.php?i=4144&c=3

http://www.dirtrider.net/gallery/showimage.php?i=4145&c=3
 
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crf250rjcd5151

Member
Dec 19, 2007
15
0
sorry for posting without doing a forum search first, this is obviously not a new topic of discussion, this was the first time I really started it at night so maybe thats why I never noticed it. So can I assume if it is running good and strong that I am ok?? if it is running lean what will I notice in the bikes running habits?? will it have a hesitation or something, what are some of the symptoms of it running lean??

Does a higher octane pump gas make that much of a difference?? seems to run pretty sweet on plain old 87.
 
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flyingfuzzball

Member
May 10, 2007
957
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i would run higher octane first off. 87 is pretty low for a high performence engine (which is what you have).

if its lean it will be harder to start. it will also bog more often.
 
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crf250rjcd5151

Member
Dec 19, 2007
15
0
I will for sure switch to higher octane, the bike runs so good, I just took it for a test ride and it doesn't get so glowing hot while your riding, the new exhuast is sweet!!!, sounds good and added a little more to the low but pulls forever now, I feel like I never need to shift, it just keeps going. Awesome!
 

whenfoxforks-ruled

Old MX Racer
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Oct 19, 2006
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Merrillville,Indiana
Cal jd jetting and tell him to hook you up with more better jetting! It sounds real rich on bottom. Are you starting it with the choke? If leaning the mixture has no effect then I would lean the leak jet. If you have to turn the mixture more than 2 turns from the stock setting you have a pilot jet issue. Is the mixture screw is still in the carb?
 
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defo26

Member
Apr 23, 2007
170
0
Is there coolant coming out of the overflow hose? If not it isnt overheating. 4-strokes headers all glow red. Get some temperature stickers and put them on the engine and see how hot it is getting.
 

whenfoxforks-ruled

Old MX Racer
~SPONSOR~
Oct 19, 2006
8,129
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Merrillville,Indiana
Naturally aspirated engines are not supposed to burn fuel in the header, this is not normal and a sign of valve or jetting issues. Stop it and you will have a lot better throttle response, go figure.
 
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Ol'89r

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Jan 27, 2000
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uh_oh

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Sep 25, 2007
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Ol'89r

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uh_oh said:
I did not know that about the valves, is this only with the new high tech thumpers or does it apply to older bikes like xr's too? is it cause by being too loose or too tight?
Click to expand...


It can happen with all four-strokes. Caused by the valves being too tight. Normally, you can't see it on the older XR's because the exhaust pipes are much a much thicker material than the new four-strokes.
 
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