Author Topic: 1983 K100RT starting/stalling issues  (Read 5978 times)

Offline rbroen07

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1983 K100RT starting/stalling issues
« on: August 08, 2017, 12:01:42 PM »

Hi guys


After reading through quite a lot starting/stalling topics here on the forum, without solving my specific issue, I hope that it is ok that I started my own... :)


I recently bought a 1983 K100RT with 75k km on it. I picked it up 200 km from home, and drove it back with no issues what so ever. I am currently in the process of stripping the bike down, as I would like to put a custom touch to it.
Intentionally, I think I will avoid using the word "cafe racer" as I am afraid of scare some of the bright K-brainiacs in here, away... well.. I just did..


Anyway... So far I have removed the fairings and installed clip ons, new headlight, and front LED blinkers. I actually did the blinker relay hack yesterday, to avoid hyperflashing..amazing what you can find in here!


[size=78%]I have only managed to drive a couple of trips on it, untill it recently began to stall after only a few minutes of driving. [/size]
The first time I experienced this, whas when I took off for a test drive around the block, without the OEM speedo cluster. I knew that the accumulator needs the cluster to charge the battery, but I thought that it would be fine for just a small trip.
The bike stalled at the first intersection during idle, and I was able to start it up right after. I limped home where it stalled a couple of times.


Thinking that this surely was because of the alternator not charging the battery, I put the cluster back on and took it out for a new drive. The same thing happened, it stalled after only a few minutes driving, and so I limped my way back home.
When I came back I could not even get it to start. When left over night it would start the first time and then stall, and not being able to start it without letting it sit for 10 minutes or so.


I then red a bunch of topics in here and on the K100 forum, about starting issues. I have tried to follow this guide:


http://hrsbstaff.ednet.ns.ca/bvogel/K100/download/bike-wont-start1.htm


During installation of new handle bars, I disassembled the throttle assembly, cleaned it and put it back together. The symptoms started after this, could be a coencidence.


Things i have tried/leaned/tested so far, to resolve the problem:


Cleaned all ground connectors
Checked fuses
Change fuel filter
Change spark plugs
Switch load shed relay with horn relay
Put contact cleaner in female connector of the EFI
Put contact cleaner in female connector of the electronic egnition unit
Tried to start with and without the TPS (Throttle position sensor/idle switch)
Tried to start without the vaccuum pipe connected to the end of the fuel rail (at the 4th cylinder).
Checked that injectors have a recistance of 16 ohms.
Fuel pump is starting when start button is pushed. I disconnected the fuel line at the fuel rail and confirmed that fuel is coming from the pump.
The Hall sensor is being fed 12v during start attempt at the connector under the tank.
Water temperature sensor giving correct resistance (ohm) at room temperature (cold bike, indoor, 20 deg celcius).
Air temperature sensor giving correct resistance (ohm) at room temperature (cold bike, indoor, 20 deg celcius).
3rd gear rool back magic trick
Battery reads 13v +
I checked that the spark plugs fires, which they do when I initially try to start it. Sencond try, 5 secs later, they do not give spark.


Also, the Halls sensors has come up in alot of the start/stall related topics, and hence I have investigated that as well. When I removed the Hall sensor, the disc/cup that is attached to the shaft,
was loose and I tightened the three bolts. I could wiggle the cup/disc from side to side, before tightening the screws. The symptoms started before I fixed this, and did not help.
It seemed as if there were wear marks on the disc where the Hall sensors are mounted.


After spending three days of testing and error seeking, it finally started yesterday after I cleaned the contact to the Hall sensor. Took it for a spin, and after 3 minutes of driving it stalled again, the same way as before.
The stalling happenes both at idle, low and high revs.


I have not yet tested the Hall sesor, and before doing so, I will try to see if I can test the cables that are attached to it.


If any of you have suggestions as what to try next, I am all ears... Thank you in advance!



PS. I have an okay sense of mechanics and electronics, and as a mechanical engineer I am keen on learning this stuff. I use a Agilent U1253A OLED handheld multimeter to test.


Here is a couple of pictures:


  • Denmark, Copenhagen
  • BMW K100 '83

Offline Laitch

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Re: 1983 K100RT starting/stalling issues
« Reply #1 on: August 08, 2017, 12:14:56 PM »
If any of you have suggestions as what to try next, I am all ears... Thank you in advance!
I don't accept thanks in advance.

Does your fuel pump use a screen basket or a fuel sock?
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Offline rbroen07

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Re: 1983 K100RT starting/stalling issues
« Reply #2 on: August 08, 2017, 01:21:34 PM »
I don't accept thanks in advance.

Does your fuel pump use a screen basket or a fuel sock?


Hi Laitch


I accept that you do not accept... :) .. also I do not know what either are, nor now to find out.. I can take a picture down the tank, would that suffice?
  • Denmark, Copenhagen
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Offline rbroen07

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Re: 1983 K100RT starting/stalling issues
« Reply #3 on: August 08, 2017, 02:14:28 PM »

Hi Laitch


I accept that you do not accept... :) .. also I do not know what either are, nor now to find out.. I can take a picture down the tank, would that suffice?
  • Denmark, Copenhagen
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Offline BrickMW

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Re: 1983 K100RT starting/stalling issues
« Reply #4 on: August 08, 2017, 02:24:54 PM »
The part in question is attached to the bottom of the fuel pump.. it is either a fairly close fitting plastic cup strainer, or a loose, more floppy "sock" that only attaches at the opening.
This is the OEM style screen..

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Offline rbroen07

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Re: 1983 K100RT starting/stalling issues
« Reply #5 on: August 08, 2017, 02:33:10 PM »
The part in question is attached to the bottom of the fuel pump.. it is either a fairly close fitting plastic cup strainer, or a loose, more floppy "sock" that only attaches at the opening.

Sent from my SM-G935V using Tapatalk


Thanks for clarifying.. I posted a picture above, taken from the tank cap.. is that enough to identify?... also I am curious as to what this influence the issues with starting stalling..


I am standing with the Hall sensor in my hands now and there does not seem to be any connectivity from the connector pins to any revealed parts of the sensor.. is that right?
  • Denmark, Copenhagen
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Offline Laitch

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Re: 1983 K100RT starting/stalling issues
« Reply #6 on: August 08, 2017, 03:20:57 PM »
... I am curious as to what this influence the issues with starting stalling..
If the fuel pump is the 52mm basket type and is mounted too low in the ring, intake of fuel gets blocked. The bike will stall. Usually, it can be restarted by moving the "choke" to partial or fully opened, but until it is adjusted to the correct height, the pump will stall intermittently.

Yours might have the fuel sock instead, but it also might have the same tendency if mounted too low. I have no experience with that type.
  • Along the Ridley in Vermont.
  • 1995 K75 89,000 miles
I wept because I had no radials until I met a man who had no splines.
https://tinyurl.com/RillRider

Offline rbm

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Re: 1983 K100RT starting/stalling issues
« Reply #7 on: August 08, 2017, 05:53:26 PM »
I am standing with the Hall sensor in my hands now and there does not seem to be any connectivity from the connector pins to any revealed parts of the sensor.. is that right?
How are you testing for connectivity?  If you are testing between any of the three wires exiting the sensor, then you won't read connectivity using a standard multimeter.  The Hall sensor has active components and a simple resistance test will not reveal anything.  You have to apply power and test the reaction of the device to the introduction of a piece of metal. Download and read these articles on hall sensors for Oilheads; it's very similar to Bricks.  http://advrider.com/index.php?threads/oilhead-hall-sensors-tech-article.50928/


Also this post on K100-forum has good information:  http://www.k100-forum.com/t5192-homemade-multifunction-ignition-timing-abs-code-reader-injectors-tester
  • Regards, Robert
Toronto, Ontario

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Offline rbroen07

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Re: 1983 K100RT starting/stalling issues
« Reply #8 on: August 09, 2017, 09:03:55 AM »
How are you testing for connectivity?  If you are testing between any of the three wires exiting the sensor, then you won't read connectivity using a standard multimeter.  The Hall sensor has active components and a simple resistance test will not reveal anything.  You have to apply power and test the reaction of the device to the introduction of a piece of metal. Download and read these articles on hall sensors for Oilheads; it's very similar to Bricks.  http://advrider.com/index.php?threads/oilhead-hall-sensors-tech-article.50928/


Also this post on K100-forum has good information:  http://www.k100-forum.com/t5192-homemade-multifunction-ignition-timing-abs-code-reader-injectors-tester


Thank you for the link, great stuff!


Just a quick question.. is it be possible to simply replace the 12 VDC LED in the test setup, with a multimeter? So, instead of activating the LED, one would simply read approximately 12 V in the display of the multimeter?


Rasmus



  • Denmark, Copenhagen
  • BMW K100 '83

Offline rbroen07

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Re: 1983 K100RT starting/stalling issues
« Reply #9 on: August 09, 2017, 05:07:14 PM »
Good evening..


I did the proper testing of the Hall sensors today, as described in various guides.. I made the setup work with some left overs from work.. it turns out that one of the Hall sensors are fine and acted as described in the guide I.e. the diode turned off when disrupted with a piece of steel.. I even did a heat test and it would keep the diode on. I used an IR thermometer to monitor the temperature and heated it up to about 150 deg Celsius. However, the other sensor I suspect is defect... when introducing a piece of metal the diode would not turn off completely.. I would recon to about 50% brightness.. It was possible to replicate the result several times... would you diagnose this one hall sensor as defect?


Rasmus
  • Denmark, Copenhagen
  • BMW K100 '83

Offline rbroen07

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Re: 1983 K100RT starting/stalling issues
« Reply #10 on: August 09, 2017, 05:44:08 PM »
greetings rasmus...

is that you in your avatar...

j o


Well hello good sir.. I am afraid so, yes... now please give me your diagnosis....


Also, is my Hall sensor dead?
  • Denmark, Copenhagen
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Offline rbm

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Re: 1983 K100RT starting/stalling issues
« Reply #11 on: August 09, 2017, 05:50:37 PM »
I would be very suspicious of the failing Hall sensor, yes. Looks like you have to replace it.
  • Regards, Robert
Toronto, Ontario

1987 K75 - Build Blog @http://k75retro.blogspot.ca/

Offline rbroen07

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Re: 1983 K100RT starting/stalling issues
« Reply #12 on: August 10, 2017, 07:10:09 AM »
I would be very suspicious of the failing Hall sensor, yes. Looks like you have to replace it.


I agree.. I have started to look for used sensors in my area.. otherwise i will have to buy a new one.. I don't think that I am up for the challenge of buying the sensors only and swapping them out with the old ones.. I'm probably just gonna buy the complete unit..


Does anyone have good experience with the non OEM sensors?




Tonight I will give my ignition a good clean... wouldn't hurt..
  • Denmark, Copenhagen
  • BMW K100 '83

Offline rbroen07

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Re: 1983 K100RT starting/stalling issues
« Reply #13 on: August 15, 2017, 03:29:31 PM »
UPDATE: I received a second hand Hall sensor today, and replaced it with the old one. And wouldn't you know..... it now runs smooth as when it left the factory almost 35 years ago... well maybe not that good, but it runs!! I tested the Hall sensors before putting it on the bike, and both sensors behaved as expected..


Now I can return to the bastardisation of the bike..  thank you for the help..
  • Denmark, Copenhagen
  • BMW K100 '83

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