My K100RT began sputtering and slowing and eventually died. This was not a sudden engine shutoff. It was very somewhat like running out of fuel. I coasted to a stop and began trying to start the engine and it would start but only run for about 5 seconds before dying again. After about 5 minutes of this it revved up and got me to a nearby store about 10 minutes down the road. I stopped for about 20 minutes and it started back up and away I went. I died again about 5 miles down the road and I started the whole process all over again. I was able to get to another store where I left the bike and got a ride home to get my truck and trailer. Currently the bike will start and run fine. This happened one other time about 6 months ago after 2.5 hours in to a 3 hour ride. Is seems to occur after a long period of riding time. Any suggestions of where to start
Mike

This is a very good description of a bad Hall sensor.
I think I posted something about this, but I don't remember when.
The easy way to test:
First, here is the most difficult part of the process: take you wife's hair dryer in the shop.
When the engine is cold, remove the cover of the Hall sensor.
Start the bike, and if it runs fine shut it off.
With the hair dryer, apply some heat directly to one Hall sensor. When hot, try to start the bike again.
If you don't find any problem, repeat with the second Hall sensor.
If the bike is still running fine, I am wrong.
If not, you just proved that one of the sensors is bad.

The bad news is that it is a very expensive part.

The good news is there:
1985-1987 k100RS Parts
Hall unit, works great, $45 Buyer pays shipping fees
Location: Reseda, Ca.
See more at http://www.flickr.com/photos/4autobahn/3073793212/
Contact Chris Telford at
Telephone 818-383-8486

I am also building a web page on troubleshooting the electronic fuel injection.
Have a look at it: Click here to see the page

Thanks for the reply - the bike is running fine now. It was actually running when I chose to leave it, but I was afraid it would stop again in a more dangerous place. It started when I got back with the trailer and loaded it, and it started this morning when I unloaded it. I let it idle for about 15 minutes and all was fine. This is really frustrating. I will try the test you have suggested and get back to you
thanks
Mike

Your story reminds me a similar one ....
My brother was in the US and during the night they had torrential rain. The morning the bike was acting like yours.
He rented a truck and took the bike back to Canada (I won't tell the whole story of his trip as it could go for pages but the total cost of the trip was $2,500).
The original K100 electronic ignition module has been recalled under warranty. IT WAS NOT WATER PROOF!
Because of the heavy rain, the water had sipped into the computer and it was shorting the ignition.
if you were traveling under rainy conditions, you should check the Moronic module for traces of water. When you close it, be sure that you put enough silicon to seal it properly.

Bert

Thanks for the tip - I have been lucky that so far I have avoided the rain, but I was sure sweating being broke down in the middle of nowhere 2 hours from home. Luckily my buddy put aside his masculine pride and hauled my sorry butt over the mountain on his k75. First time on the back for me -- hopefully the last.

Hi Mike, the other thing it sounds like to me is the classic case of the fuel in the fuel lines "boiling" and exactly the same thing happened to me and has not repeated itself.
There are a lot of posts regarding this problem and the RT would have to be the most prone to the fault due to stupid proximity of the fuel line to the top radiator hose and the lack of airflow around the tank. What were they thinking?
At the moment I am steadily working through a number of ideas to cure the hot tank problem.

Regards,

Phil

interesting thing that you mention this because I thought of that when the engine died. I immediately felt the tank and it was cool. I opened the gas door and touched the fuel and it was cool. Could the gas be boiling in the fuel lines with the tank cool?
Mike

The indication on mine and others is a warm to hot fuel tank. The fact that your tank is cool and the fuel also probably suggests otherwise.

I was also thinking that it is only just Spring in the Northern Hemisphere so I am not sure of the weather at "the dragon" but I am guessing it is still relatively cool.

The other suspicion with mine, as I was fairly new to the model at the time, was the fuel pump so I replaced it with a second hand unit and the problem has not re-occurred.

Nothing like an intermittent fault to makes those rides interesting.

Regards,

Phil

I warmed up the engine until the cooling fan was cycling repeatedly and placed a hair dyer over the HES. Kept the heat on for about 15 minutes and the bike did not exhibit any problems. Placed the cover back on the HES and got on an rode the brick pretty hard for about 5 miles -- no problems. I guess I should be relieved because is appears the HES is OK, but I am still at a loss...will begin removing the tank to check the fuel lines and replace fuel filter and maybe fuel pump.

Who knows maybe it was just a bit of bad fuel although I know my tank had a fair bit of "gunk" in the bottom of it which was not doing the strainer any favours.

Apparently the rubber mounting for the pump can disintegrate so taking it all out and having a look won't hurt.

The vent lines are also worth checking just in case of blockage as opening the tank also equalises pressure and can hide the problem.

Regards,

Phil

new developments - after removing the filter and pump I found that the filter was almost completely shut off. Very little air can be blown through the filter. The pump damper is like goo, and a black goo is loose in the tank especially near the pump intake. Any suggestions on how to clean the tank. Every crevice has some goo in it.
Mike

OK you want a bad answer.... crack a match in the tank and after 3 seconds it will be super clean...

Now being a bit more serious, I don't have a real answer but you are talking about goo, and here in the schools, the cleaner are using a product called "GooGone" The product is manufactured by Magic American Corporation and I am very impressed with its power. I strong enough to remove permanent marker graffiti on a wall I t would be worst trying it if nobody provides another answer.

If you have to replace your fuel filter, you may also want to check one of my article:
Goto: http://www.bmwons.ca/ Click on the left tab "Technical tip" and find my article on fuel filter replacement on a K75 (same as K100)

Bert

In my excitement I only read the first line of your post --- oh well, I didn't need eyebrows anyway
just kidding - it appears the black gunk or goo is the remains of the rubber pump damper. Would there be anything wrong with cleaning the tank with a high pressure water hose? Thanks for the tip
Mike

Mike, This goo was the result of the gas dissolving the rubber.
Why don't you try first to scrub it with a nylon scrubbing pad and some gas. The gas may dissolve the rubber again.
This would be my first try.
Sorry about my first comment but it was so easy.
People knowing me know what to expect to come out of my mouth.... Not always what you are expecting!

Let us know how you are making out.

Bert