Glowing exhaust - K-Bikes.com - Excellence in Motion
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post #1 of 16 (permalink) Old Mar 3rd, 2010, 7:19 pm Thread Starter
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Glowing exhaust

Hi, I'm new to the forum. This is my 3rd BMW, a 94 K1100LT.
Got a problem here in that the exhaust is glowing at the catalic converter.
The fuel pressure regulator has been replaced as well as the exhaust. Both were purchased pre owned.
Thank you for any troubleshooting info.
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post #2 of 16 (permalink) Old Mar 3rd, 2010, 8:09 pm
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Yes, there was a thread like that on ADVrider not long ago,the Glow in the Dark thing. They did not seem too worried about it, them things get pretty darn hot inside. I'll go there later and see if I can dig it out.

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post #3 of 16 (permalink) Old Mar 3rd, 2010, 8:30 pm Thread Starter
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This thing would look like a torch in the dark, day time it glows cherry red!!!
It also had a decrease in power when it began.
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post #4 of 16 (permalink) Old Mar 4th, 2010, 1:06 am
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I went and checked that other forum, he was getting too much fuel into the cat from a hung throttle cable, can't be your problem here. But I have seen another guy where the cat actually "Melted" not physically of course, but that is the term used in the industry. But the first guy had actually melted his tire....

What I would do first is to take the exhaust right off and run it like that for a couple minutes, then look at the exhaust ports to see if there is unburned gas in there. It will be noisy....I remember starting my K100RS like that just out of curiosity, may try the K1200RS soon! And keep your hand on the kill switch and a fire extinguisher handy.

Mind you you may get some clues just by removing the exhaust, like traces of unburned fuel in the headers.

But if there is unburned fuel in there, then I would look at the rest of the fueling system, you can probably test the fuel pressure Etc...I don't have the method here but certainly possible.

Stuck/defective TPS ?

Mouse nest in the exhaust...don't laugh that one happened to me years ago!

No fuel in the exhaust, then the cat is most probably plugged/melted. Do you know a good welder/surgeon?

But I am wondering as to why the parts like fuel regulator were replaced in the first place? Was there another problem and changing parts just compounded it? Was it acting up before? Details please....!

Benelli 50cc at 14
Yamaha RD 200 at 16
Yamaha RD 350 at 17
Honda CB 750 F at 18
Honda V45 Sabre at 24
BMW K100RS at 27
BMW R100GS at 34
BMW K1200RS at 53

Last edited by h96669; Mar 4th, 2010 at 1:11 am.
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post #5 of 16 (permalink) Old Mar 4th, 2010, 9:07 am Thread Starter
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My neighbor (who was buying the bike (he now has twins and I have the bike back) was riding home when it began loosing power and smelled hot. Looked down and the exhaust was cherry red. Bike had been running fine and ridden weekly.

Air filter ok,

Puel pumping, not sure of psi.

He had cut off the mufflers and replaced with 2 open pipes with baffles can't believe he did that!!!

Still glows red hot.

I now get bike back because he now has twins and replace the fuel psi regulator as poss for causing a lean condition (pre owned part).

Still glows red hot.

Replace the exhaust with a stock unit (this is a BMW, not a crotch rocket!!!).

Still glows red hot.

I'll see what I can come up with concerning the TPS.

Not sure what else I could check before taking to a dealer.


Last edited by 2QMedic; Mar 4th, 2010 at 9:13 am.
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post #6 of 16 (permalink) Old Mar 4th, 2010, 12:29 pm
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Hi,

Did a bit of searching, not much comes up on that, a few on K1200LTs with broken cats that had to be replaced, one also where thay had to replace the Motronic brain to cure that, but he may have had other issues too contributing to the failure of the brain.

However, you are giving me a clue, re exchanging them exhausts....running with "straight pipes" may have cooked the O2 sensor, that would certainly cause all sorts of mixture problems. Looking at the parts fiche, if that bike has a cat, it has to have a O2 sensor.

Your neighbor ran straight pipes.....did he also ran leaded race gas in there....! Ooops...not good for Cats and O2 sensors!

So...question here, was the O2 sensor removed when converted to the straight pipes?
If not then the brain may have learned some bad habits....that may take some miles to clear out, and that is after installing a new O2 sensor and resetting the TPS.

That BMW sensor is mucho $$$$, but can be replaced with a Bosch Universal at a fraction of the cost.($60.00)That would be Bosch 15730, you will have to splice it in there but that is easy, and a very long thread on this site on that one.
http://www.k-bikes.com/forums/showth...1&page=3&pp=10

But here is a test you can do to see if yours is doing what it should:
http://www.ibmwr.org/ktech/O2-sensor-testing.shtml

But....if everything got as hot as you said, I think the sensor is cooked/toast!

I have always been suspicious of used electric/electronic parts, if they have any wires attached to them I stay away, most of them are hard to test so used parts dealers give exchange warranties, but there is always the odd shyster trying to recoup his investment in new parts....

Good luck!

P.S. now he has twins....he is getting back what you guys got from the "neighbor with straight pipes"....I've been there!

Benelli 50cc at 14
Yamaha RD 200 at 16
Yamaha RD 350 at 17
Honda CB 750 F at 18
Honda V45 Sabre at 24
BMW K100RS at 27
BMW R100GS at 34
BMW K1200RS at 53
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post #7 of 16 (permalink) Old Mar 4th, 2010, 4:21 pm Thread Starter
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He cut off the exhaust after the over heated condition and never rode it after that. He thought that the inside of the muffler may have been comming apart. He replaced the mufflers, the O2 sensor was left in place, he ran it up the rode, exhaust still red and returned.

I replaced the fuel pressure regulator (used) and figured what is the chance of it being bad also??? But with that and the complete exhaust replaced-it's still hot???

I agree that sensor is probably toast.

Thanks for the reading material, I've never had to dive deep into any BMW that I have had in the past.

I was suprised not to find a thread for this from some one else???

As far as the neighbor, he brought the bike back over and will have nothing to do with it concerning trouble shooting (he was a mechanic for much of his life). It's fustrating!!!

But the twins are keeping them busy. I realy am glad for them, they tried for many years.

thanks again
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post #8 of 16 (permalink) Old Mar 4th, 2010, 4:31 pm Thread Starter
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I was just thinking, it the O2 sensor is toast, would that cause a leaner or richer condition??? or would it be a toss of the coin???
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post #9 of 16 (permalink) Old Mar 4th, 2010, 5:35 pm
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I'm no expert on them O2 sensors, but mine is the 4 wires style so has a heater in it and those take a few minutes to kick in. What I have noticed is that my bike is very rich on start up to the point of smelling of raw gasoline but goes back to normal after a few minutes. I assume the heater is what does the leaning, so once it kicks in the mixture goes leaner.

I had them testing instructions, looked at them but for peace of mind I just changed the sensor. Did not change much on the bike at 20,000 miles, but what the heck was only $60.00 bucks. At about the same time I had to look at my friend's Toyota pick-up running rich too, it had two O2 sensors at $130.00 ea. aftermarket....but Toyota bought it back because of a rusty frame.

I changed the one on my old Chevy to correct an intermittent "Rich Mixture" fault code at idle, kept getting the same code, changed the pressure regulator.....still got the same code but less often, never had the chance of finishing that one, the head gasket blew up not long after and destroyed the engine.

So.....I'm interested in your thread, I feel I have some unresolved issues with them Cats/O2 sensors.....going way back to the 70's when we had to tow a couple cars where the cat plugged up, swelled and set the carpet on fire. And that was always from the owner removing the belt for the air pump, cutting the cooling air flow to the cat.

Benelli 50cc at 14
Yamaha RD 200 at 16
Yamaha RD 350 at 17
Honda CB 750 F at 18
Honda V45 Sabre at 24
BMW K100RS at 27
BMW R100GS at 34
BMW K1200RS at 53
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post #10 of 16 (permalink) Old Mar 5th, 2010, 3:03 am
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First thing I might do is compare the exhaust gas temperature at the spout with another LT. The CAT is mean't to run hot, so the surface temperature could be checked too after both bikes had come off a short ride.

Are you sure the CAT is actually present inside? I've read of some who found some very neat TIG welding where the CAT had been opened up and the element removed.

What mpg are you getting? that might give a clue to over rich mixture, any performance chip fitted you don't know about?

Has somebody done a valve re-shim and screwed up the valve timing?

Then I'd also look at the ignition timing advance. It's tricky to do and a lot easier with their computer diagnostics, In fact the whole problem is probably easier to understand with a diagnostics check first.



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