Hello everybody , 
i want to share with you an experience that i have. First of all excuse my English i might write something not so understandable.
    I own an 1987 K100 naked for the last 3 years. The motor was singing like a bird , lot of plesant km till beggining of this winter that i decided to make some body work. I took it to my mechanic to prepare her for being idle for some time. i took the bike to my place that i was supposed to make the body work and i started.
    The result was quite nice


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But after starting her up the problems came. Although it was starting immediately and easy , when i was touching the throtle the engine was dying. 4 times my mechanic took her and 4 times , after 4-5 km was happening the same thing. The thing that i remember that the mechanic was doing was to open the air filter , teasing something with his fingers on the air flow meter , and the engine was running. He was taking it to his place and after a day or two the bike was coming back ''FIXED''.... but nothing is fixed. The same thing again and again. I decided ,after some events , that my mechanic does not have a clue how a K motor is working. So i started dealing all by myself. 
injectors - cleaned
new filter
new fuel pump
and ...comes the matter of air flow meter.
Has never been opened. I have no idea what to do with it. As it seems all the problems comes from that. i read all the topics obout, i opened it and studied it , but still couldnt do anything.
Can someone give a help hand ??

hi there .

have a look on the portal page for the "efi electronic ignition trouble shooting "

you will find all sorts of information about the afm in there

cheers

Welcome to the forum.

That's a very nice K you have, looks really good and you take good care of it.

So what did your mechanic do to prepare the bike for being idle for some time?

Was the low seat on the K when you bought it or did you do that?

When the bike starts and then cuts out after 4/5 km will it start again and tick over? Or will it start and cut out when you take your finger off the button?

may not be airflow meter at all ...

could be temperature sensor  on the water stub and electrical connections to this

What my mechanic did ? ... Just took from me 200 E as it seems  
The seat i fixed it. I also placed windshield and laggages.
The bike is working for 4-5 km and then dies. it starts but can't get more than 1500 rpm. If its cold, you toch the throtle and it dies. If its warm you game with the throttle but just wont give rpm.
I read the topic about the EFI but still can't figure out what is going on. i believe that there's something wrong with the electronic system into the air flow meter

Because of the age of the K there can be an issue with electrical connections rather than components. Don't be too quick to suspect the air flow meter. The bike is starting, its getting fuel, for 4/5 km it is working properly. Everything worked properly until you did the body work.

So, what was done to the body work and what did the mechanic do? These might let you look at any electrical connections you were working on, under the seat, under the petrol tank, connections to fuel pressure regulator, connections to temperature sensor [I though this would not cause a cut out if it activated while running, instead would not allow a restart].

92KK 84WW Olaf wrote:Because of the age of the K there can be an issue with electrical connections rather than components. Don't be too quick to suspect the air flow meter. The bike is starting, its getting fuel, for 4/5 km it is working properly. Everything worked properly until you did the body work.

So, what was done to the body work and what did the mechanic do? These might let you look at any electrical connections you were working on, under the seat, under the petrol tank, connections to fuel pressure regulator, connections to temperature sensor [I though this would not cause a cut out if it activated while running, instead would not allow a restart].

every plug was carefully cleaned and placed back. Of course can be a bad connection and i wonder how could i find it, but i think that if there could be prob with that the bike wont work at all. Why after teasing the moving part of the flow control it works for some time ?

I had a problem like that and some others have had problems like that too and they will give you some very good posts when they come on line. Don't give up on it because it almost always is something very simple. The reason I asked about the low seat was that there is a unit under the seat that is known to sometimes have a problem with connections, as in all the pins. The K gets its signal from 2 sources, one is when you press the starter button and that is working fine, the second is after then engine fires and its also getting the second signal because it will run properly, but only for 4/5km. Something is either causing the electrical system to lose its spark or the fuel system is losing pressure or something is cutting off the fuel supply [a partially blocked fuel filter or faulty fuel pressure regulator].

I had a problem with an air flow meter in my car and cleaning was not really an option as it rarely worked, replacement was advised and to stay with the Bosch unit. But don't go buying one until someone with a lot more knowledge than me comes along and tells you to do that.

There have been strikingly similar symptoms with other members machines. Two just recently. One of those and another a while back seems to be there was an aftermarket immobiliser installed that after years had malfunctioned/shorted.
Can you identify any electrical modifications that may have been done by a PO?
This would likely be in the electrical box under the tank.

very true olaf
did you mean the fi relay   as the second source....we have seen these relays not function recently ...in a few posts ...and all put down to the under tank icu  not grounding out the relay for the function ...when it should be  ... this is sometimes related to the hall effect sensors ...which send pulses to the icu ...if the pulses are not received then things go wrong ......
having said that ...we know that sometimes the hall effects do become temperature sensitive .....and my best guess is that this sounds like a good candidate ...in the fact that it only runs for a few minutes  then dies  ( as heat is experienced ?)



but also if the under seat computer connector  comes loose it certainly will die ...I have experienced this as an intermittent functioning ...and when some extra vibration occurs it did .

just a click to make it sit properly ....after bending the retaining clip so it locked home properly

the under seat connector is where you an test a few things ...look at the circuits and diagrams

to test the temperature sensor ...test with meter on ohms  10,000  or 20,000  between pins 10 and 13 (earth)  at cold should measure about 3000 or so ...as it warms it gets less


whilst doing this ...shake move the terminals to the temperature sensor connector



just out of interest ....has an inspection been done to confirm that there hasn't been any pinching of the cables between the frame and seat ,,etc ?


just some ideas

The bike is working for 4-5 km and then dies. it starts but can't get more than 1500 rpm. If its cold, you touch the throttle and it dies. If its warm you game with the throttle but just wont give rpm.

OK guys, here is a quiz:

What component signals to the fuel management that the throttle is shut off?
The throttle position switch (TPS)


___________________________________________________________________________
The TPS is located at the end of the fuel injector rail. It will cut-off the fuel injector when your are releasing the throttle.
With this system, when decelerating, the fuel injection is disabled until the rpm goes down to 2000rpm. If the engine is still decelerating and the rpm is lower than 2000, the EFI is re-enabled and the injection is controlled again by the FI computer.
___________________________________________________________________________

What if the idle switch (1) in the TPS is defective (maybe sticky) and signals to the EFI that the throttle is off even if you are accelerating?You won't be able to pass the 2000rpm.

My solution would be to disconnect the TPS and see if it solves the problem.

If it was a problem with the HALL sensors, the bike would run on 2 cylinders but xatzigiorgis has not mention this kind of problem

92KK 84WW Olaf wrote:I had a problem with an air flow meter in my car and cleaning was not really an option as it rarely worked, replacement was advised and to stay with the Bosch unit. But don't go buying one until someone with a lot more knowledge than me comes along and tells you to do that.

Keep in mind that the air flow meters on the older Ks are mechanical and wear differently that the modern car's hot wire anenometer, so they are prone to age-based failure. Physically wiping a metal contact across a conductive surface is a solution that normal usage will eventually cause to fail. There's not too much to simply spray down and clean in them. On the plus side, you can test them pretty easily.

As it seems my problem is at the TPS ...
The air flow meter seems to work nice. I m trying to open the TPS unit but without good result. Somehow it does not open.

xatzigiorgis wrote:As it seems my problem is at the TPS ...
The air flow meter seems to work nice. I m trying to open the TPS unit but without good result. Somehow it does not open.

Just unplug it to test first.
If that solves your problem, you can open it after. The TPS is not essential and a lot of us have it unpluged.

Tom had a problem a little similar to this
https://www.k100-forum.com/t9165-difficult-to-start-when-cold#108141

This is the post where he reported the fix
https://www.k100-forum.com/t9336-another-k100-joins-the-shed#110118

Crazy Frog wrote:

xatzigiorgis wrote:As it seems my problem is at the TPS ...
The air flow meter seems to work nice. I m trying to open the TPS unit but without good result. Somehow it does not open.

Just unplug it to test first.
If that solves your problem, you can open it after. The TPS is not essential and a lot of us have it unpluged.

Now you mention it ... when i was doing my tests i forgot to plug it and the bike waw working. After plugging it and started again the probs , i removed it once more but without any effect. may be i should have removed the battery to reset the possible errors ???

EUREKAAAAA ....
We found the problem and it's the injection unit (under the seat) !
The case is where to find it ...  :pale: