98 R1100RT glowing red headers!!

So, I used my throttle lock to let my R1100 idle at about 3000 rpm, while it sits in my driveway. I did this for no more than 90 seconds. I was trying to see how bad it would 'surge'. The oil temp raised to only 1 bar. I shut it down and the headers are glowing bright red! Is this a normal thing for such a short period of time? Maybe my fuel mixture is off?? and thats why I can't stand riding this bike slower than 50 mph? Or am I just looking for problems that don't exist?

Short answer: They all do that.

Long answer: There was no air stream cooling the headers. Don't do that again...without pics.

jhgilbert said:

Short answer: They all do that.

Long answer: There was no air stream cooling the headers. Don't do that again...without pics.

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And a fire extinguisher. The notable case was bike, car, garage, house ....

Do I detect a beer story in that reply?

Not a good idea to ever let an Oilhead sit running without airflow over it, especially at elevated rpm. 90 seconds? Bet it was longer than that. But that is beside the point as the bike will not surge sitting in place with the throttle locked. Too many other factors are part of it. If your bike surges during steady state riding at 3,000 to 4,000 rpm, you know it surges. So a stationary test really tells little of nothing.

Surging on the post 93 and 94 Oilheads is basically caused by a lean fuel mixture at partial steady state throttle. The early Oilheads ran a bit more rich all the time and did not surge (my 94 RS has never exhibited surging). After 94 BMW changed the fuel mixture to be more lean for emissions and the surging developed. One easy change that "may" work on the 98 Oilhead is to change the CAT CODE plug to a pink color, which modifies the fuel mixture. Worked on the 95 to 96, but I'm not certain it applies on the 98.

oldnslow said:

. The oil temp raised to only 1 bar.

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What temperature gauge do you have????

The headers will get hotter faster than the oil, especially since the oil has a cooler, and part of its purpose in life is to carry away heat anyway. But yeah, don't do that without some decent airflow over the head and pipes.
And yes, the surging (if you've got it) is best experienced under load. Put it in 2nd and go up a slight but long hill at about 2500 rpm. Let the engine fully warm up first (at least 4 and preferably 5 bars on the RID) to get the real picture, "cold" is not accurate information.

I can't think of a better way to waste your motor. Have fun!

Watch out!

My friend did this same thing, many years ago now and MELTED his RT fairing around the pipes area. I don't think any harm came of your glowing pipes, but the heat surrounding them is harmful to fairing, I saw it myself. Single wall headers are a trademark of BMW and perhaps some other bikes too, but they glow very easy with no air flow. 3000rpm at idle for even a short time is a bit risky, but the 4 quarts of oil keep lubrication flowing quite well. Your fairing would be your biggest concern. Randy

Polarbear said:

My friend did this same thing, many years ago now and MELTED his RT fairing around the pipes area. I don't think any harm came of your glowing pipes, but the heat surrounding them is harmful to fairing, I saw it myself. Single wall headers are a trademark of BMW and perhaps some other bikes too, but they glow very easy with no air flow. 3000rpm at idle for even a short time is a bit risky, but the 4 quarts of oil keep lubrication flowing quite well. Your fairing would be your biggest concern. Randy

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I've had customers warm up their boxer inside a garage and walk away for supposedly a few minutes and melt their oil sight window. End result? Wasted motor. My guess is they walked away for a lot more time than they think.

ANDYVH said:

Not a good idea to ever let an Oilhead sit running without airflow over it, especially at elevated rpm. 90 seconds? Bet it was longer than that. But that is beside the point as the bike will not surge sitting in place with the throttle locked. Too many other factors are part of it. If your bike surges during steady state riding at 3,000 to 4,000 rpm, you know it surges. So a stationary test really tells little of nothing.

Surging on the post 93 and 94 Oilheads is basically caused by a lean fuel mixture at partial steady state throttle. The early Oilheads ran a bit more rich all the time and did not surge (my 94 RS has never exhibited surging). After 94 BMW changed the fuel mixture to be more lean for emissions and the surging developed. One easy change that "may" work on the 98 Oilhead is to change the CAT CODE plug to a pink color, which modifies the fuel mixture. Worked on the 95 to 96, but I'm not certain it applies on the 98.

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+1 on all the above.
to get those pipes glowing red, it was substantially more than 90 secs. If you can confirm the elapsed 90 secs as accurate, i'd look to do a valve adjustment, as that brief amount of time is not sufficient to produce that result with a properly adjusted bike.
to feel/experience surging requires running under load, not idling. most common surge range is 3-4K.
do yourself, and your bike. a big favor, and don't repeat that experiment.

bikerfish1100 said:

...do yourself, and your bike. a big favor, and don't repeat that experiment.

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...but if you do, make sure you've set up the video camera beforehand.

This advice applies to ANY air cooled bike. My V twin, by DRZ, etc. It it aint got a water cooled radiator, it's bad!

I think a lot of people, especially younger people, who only have cars or water-cooled bikes forget what we old guys learned long ago.

In addition to all the good points made already I'll add that the very hottest exhaust temperatures (peak EGT) occur at lambda=1 which is 14.7:1. This is exactly the point that the stock narrowband O2 sensor controls to. A richer mixture is cooler and surprisingly a leaner mixture is cooler (see chart below). The richer mixture has excess fuel cooling things and the leaner mixture has excess air. So I guess you could say our bikes are designed to have a red-hot exhaust.

The primary cause of surging is a left/right power imbalance caused by unequal fueling, assuming that you've done a good valve adjustment and throttle body balance. BMW didn't really solve this problem until the R1200 bikes that have dual O2 sensors. With the two O2s and BMS-K fueling computer it makes the left/right fueling nearly identical. On the 1100, if your fuel injectors are unequal, there's no way to equalize AFR. On the other hand if the injectors are close, a careful valve and TB tune will improve things.

AndyVH mentioned switching to the Pink coding plug. The fueling between yellow and pink will not be so different since they both fuel to 14.7:1 per the same O2 sensor. The Pink plug is for the GS engine with 10.3:1 compression where the Yellow RT plug is for an engine with 10.7:1 compression so it seems more likely to me that the Spark Advnace is different.

The best coding plug for an R1100RT from the standpoint of surging seems to be No Plug since then the Motronic doesn't use the O2 sensor. Without a plug though you should probably add a CO potentiometer so that you can manually adjust the idle mixture.

Last thought on surging on the 1100 would be to shift lambda on the stock sensor like Happy Wanderer did after a long period of experimenting with all the above. http://forums.bmwmoa.org/showthread.php?56990-2004-R1150RT-Wideband-O2-Sensors&p=880407&viewfull=1#post880407.