Hey all.
My K100RT was bricked for over 7 years till a couple of months ago.
When got it up running the LCD display on the instrument cluster was displaying 4 with the bike in Neutral. Also the N(eutral) light was off.
After reading and studying i decided to get a secondhand one from Motorwoks.uk and passed it to my mechanic to replace it since i was affraid to dare removing the swingarm at my backyard prior replacement.
Mechanic did the swap (he had to change the plug, mine was the early transparent one, the sensor had the black one) and informed me that it worked so made me happy.
After a couple of days went to get the bike from the mechanics garage.
Sensor was not working at all. 
Not even displaying anything on the LCD screen. Totally blank, no Green Light ever.
So i started the troubleshooting myself.  
Removed the 4 cables of the plug ( to the instrument direction )
tried several combinations of grounding the cables each to other and got Green Light (N) and all of the gear numbers displayed on the instruments LCD.
Next step was to mess with the other plug, the one to the GPI switch (the one the mechanic had replaced) He actually did no cuts, he just pulled the pins out of the old transparent and installed em into the new plug.
Found out that the Yellow white one was unsoldered from the pin. Thought that this was the problem. So in draft mode i put the 4 stripped cables of the GPI switch side to the 4 cables of the instrument cluster side. 
Blank again. Nothing. 
While messing with the cables i sensed excessive temperature in my fingers from the cables. Smelled something burnt.



After that moment, no clock with the ignition switch off ofcourse. 

Any ideas on how to solve this out? Maybe something to take into account is the old alarm system removal (non BMW alarm) from an electrician in the meanwhile.
I have ordered another used GPI from Motorworks and and a a fully working instrument cluster too.. But i need to make sure that there is no electrical problem before installing them

Can you pull the rubber mat off the pins please and take a picture of the PCB underneath?

Dai wrote:Can you pull the rubber mat off the pins please and take a picture of the PCB underneath?

Thanks a lot Dai. I m messaging you

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This is the deeper I can get . Terrible smell also.




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Not to put too fine a point on it, that PCB is shafted and - as usual (! ) - Inge was right about the source of the problem. My bet is that Motorworks in the UK will have a spare secondhand PCB. Give them a ring on

+44 1484 353600

- or fill this request form in: https://www.motorworks.co.uk/vlive/Help/PartsQuoteEnquiry.php

A lot of their secondhand stuff is not advertised on the website.

Dai wrote: My bet is that Motorworks in the UK will have a spare secondhand PCB.

As you have the version with 4 & 7 liter low fuel level warning lamp you
should have part # 62 11 1 459 902.

Inge K. wrote:

Dai wrote: My bet is that Motorworks in the UK will have a spare secondhand PCB.

As you have the version with 4 & 7 liter low fuel level warning lamp you
should have part # 62 11 1 459 902.

No available parts from Motorworks.uk. not even used.
Found a K75RT instrument complete and in great shape. 
besides the fact that it has the round pins instead of the flat ones like mine ( as i read it fits ) i m reading that maybe there is some differences in wiring of the 7L -4L lights.
Do you know anything about it?
Thank you

Then you must swap the PCB for the low fuel level warning as the K75 have
a different sensor.

This PCB you find behind the tacho in the top/outside corner, it's shaped like an r.

Nice Is PCB swapping a relative easy task to perform?

Something more. Still trying to understand what's going wrong with the GPI switch ( transmission side )

Ignition switched off
Gear selector in neutral
Using my electronics multimeter in beeper ( resistance mode )
Shouldn't I get closed circuit beep if close circuit between brown cable and a ground?
Or I m in a completely wrong approach ??




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George_Pap wrote:Nice Shouldn't I get closed circuit beep if close circuit between brown cable and a ground?

Yes you should, on this brown wire.....

On that brown wire you ve pointed ( towards instrument ) I m getting closed circuit reading and beep.
But I m trying to figure out a way to test the sensor' s operation without removing the swingarm etc ..
So I guess the only way is to do so.

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Then this could become useful......

http://www.ibmwr.org/ktech/trans-switch.shtml



Or this one, if its easier to interpret.....

https://www.k100-forum.com/t6936-gear-position-switch#79607

George_Pap wrote:Nice Is PCB swapping a relative easy task to perform?

As you must change the blue conductive film and related plastic part it isn't
that much work....four small screws on PCB and a one on the transistor.
(I assume you only have the 4L transistor as you model is close to the date
for the change of the sensor system).

It's a heatsink for the transistor glued on the rearside of the tacho, you must
make something similar.....or swapp the complete tacho together with the
GPI and fuel level PCB's.

Inge K. wrote:Then this could become useful......

http://www.ibmwr.org/ktech/trans-switch.shtml

Thank you!! I will give it a try!!

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George_Pap wrote:

Inge K. wrote:Then this could become useful......

http://www.ibmwr.org/ktech/trans-switch.shtml

Thank you!! I will give it a try!!

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One more link have been added to that post.

Inge K. wrote:

George_Pap wrote:Nice [smiley]https://2img.net/i/fa/i/smiles/icon_smile.gif[/smiley] Is PCB swapping a relative easy task to perform?

As you must change the blue conductive film and related plastic part it isn't
that much work....four small screws on PCB and a one on the transistor.
(I assume you only have the 4L transistor as you model is close to the date
for the change of the sensor system).

It's a heatsink for the transistor glued on the rearside of the tacho, you must
make something similar.....or swapp the complete tacho together with the
GPI and fuel level PCB's.

Hmmm. If I get it correct, on the tacho back is where the fuel level PCB s are located ? Cause the fuel level bulbs 7&4L are located on the left Speedo instrument.

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George_Pap wrote: If I get it correct, on the tacho back is where the fuel level PCB s are located ?

Yes.

All right! , homework for the weekend

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Good Luck .

Thank you!! I ll keep you updated
I hope I m getting close to ressurection day. And the help from you people.in this forum is really more than appreciated and valued!

I m waiting for the motoworks shipment

a rear disc rotor (brembo)
Original fuel pump and fittings
Used Fuel sender unit
Front brake pump repair kit
Used GPI sensor

And some bodyworks to the right side

Hope nothing else pops out



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Here is a third link, two first in post #12.

https://www.k100-forum.com/t10495-gear-indicator-board-for-1985-k100rt-instruments#124102

George_Pap wrote:Something more. Still trying to understand what's going wrong with the GPI switch ( transmission side )

Ignition switched off
Gear selector in neutral
Using my electronics multimeter in beeper ( resistance mode )
Shouldn't I get closed circuit beep if close circuit between brown cable and a ground?
Or I m in a completely  wrong approach ??

No, you normally don't have continuity between that Brown wire and frame ground when measuring the continuity with the plug disconnected. That wire is the TGPI switch common lead and you should get continuity or absence of continuity between it and the three other wires on that switch. Once you plug the switch back into the harness, ground is applied to the brown wire.

robmack wrote:

George_Pap wrote:Something more. Still trying to understand what's going wrong with the GPI switch ( transmission side )

Ignition switched off
Gear selector in neutral
Using my electronics multimeter in beeper ( resistance mode )
Shouldn't I get closed circuit beep if close circuit between brown cable and a ground?
Or I m in a completely  wrong approach ??

No, you normally don't have continuity between that Brown wire and frame ground when measuring the continuity with the plug disconnected.  That wire is the TGPI switch common lead and you should get continuity or absence of continuity between it and the three other wires on that switch.  Once you plug the switch back into the harness, ground is applied to the brown wire.

thanks

Inge K. wrote:Here is a third link, two first in post #12.

https://www.k100-forum.com/t10495-gear-indicator-board-for-1985-k100rt-instruments#124102

Looks like this is my case Inge. I recall the mechanic that swapped the first GPI switch telling me that it worked initially but when he finished assembling the swing arm back in place he got blank lcd screen.

As already concluded earlier in this thread, the problem is in the instrument
cluster (and the switch is probably OK).
It have been a short between Pin 1 (clock) and 2 (GPI switch) and the pins
also seems to be missing.

You say in the first post that you got 4 in neutral, and that is typical when
connection at pin 2 (yellow/white) is missing.

When connection at pin 2 is missing you would get:
1 = 5
N = 4
2 = blank
3 = blank
4 = 4
5 = 5

I guess i made some newbie mistakes but please forgive me. I will try to put the situation in a timeline to make it easier (!) to come up with a solution.

November 2017
Bike get to the Mechanics Garage. ( visit #1 ) 
---------------------------------------------------------
Condition when in : Bike bricked. 8 years off. No run. GPI switch problem, No Neutral Light, number 4 only when in N but cant recall any other numbers since i drove it just once till then

Works performed :

- Engine Oil & Radiatior fluids change
- injectors ultrasonic cleaning
- Air filter cleaning
- Fuel Pump replacement with a chineese, no branded cheap (60euros) one, modifications made to cables inside the fuel tank prior fitting the new pump.
- Rear Brake fluids - Rear pump was defective, needed swap.
- Battery changed with a 18AH 

Condition of the bike when left the mechanic: 
Gpi: As before
Throttle grip very tight
Almost no rear brake, fluid was leaking from the broken fluid tank, also the pump was leaking.

December 2017
Works in my backyard 
Took the instrument cluster off so i could check for N light and corrosion inside. It was like brand new, not even a tiny sign of corrosion / humidity etc. Glowing and super clean like new. Fixed just the 4L cover glass that was missplaced a bit. Was easy. Pins inspected, everything perfect!
Took it for a short ride but since the tires were 9 y'old after some engine strange behaviour like dropping rpm cut outs my K slipped and dropped to the right side fortunately with less than 5km/h in a turn.


January 2018
Bike get to the Mechanics Garage. ( visit #2 ) 
---------------------------------------------------------
Ordered from MotorWorks some stuff as:
New rear brake pump
New brake fluid pump
Used GPI switch 

Rode the bike to the mechanic ( distance 15km ) at very low speed (less than 50km/h) due to tires fear. At the 13th km of the ride bike engine stalls, like fuel cut off till totally off. Starting again immediately with 2-3 tries with the starter , ride for 100-200 meters, same behaviour again.
Managed to get to the mechanic though

Works performed at the 2nd visit to the mechanic:
- Tires change to Bridgestones BT45s
- Swap of the GPI sensor
- Seek for the cause of the engine problem. 
- Doberman Alarm uninstallation
- Rear Fuel Pump / fluid tank Swap with the new ones
- Spark plugs swap ( with a corresponding type not the original ones )

After a month (!!) of seeking the problem with the engine cut off problem he comes up with a verdict that the problem went off when he tuned some screw under the airfilter box (?) probably the fuel mixture? as he said.
i gave him direction i got here to check the Hall Effect Sensor and said it was ok. (heat gun test) 

Took the K home. Ride was smooth no problems. The GPI now is totally blank in the LCD. Mechanic stated that it worked initially but when he took the bike off the service stand it went blank again.  Also the electrician stated that after uninstalling the alarm system the bike was now starting so he had to work a lot with the cables under the fuel tank in order to get it back running.

Next day with new tires on decided to take my bike to the painter works to fix the broken right hand mirror and the right hand lower frame part that was broken.

key on, kill switch on, starter firing up but engine dead  After 5 minutes trying the battery was dead.
tried to charge it off the bike but no luck. No more than 11.5V right after 10 hours of charging.
With the dead battery on i just had instrument cluster lights and indicators on so until the purchase of the new battery i though it was a good time to mess with testing the GPI problem.
Took out the pins from both plugs and started experimenting by various combinations closing circuits between each cable with the other ( towards Instrument cluster ) until i got the green light on and all the numbers displayed on the LCD screen. BUT in a certain combination (dont recall which one exactly ) i felt excessive heating in the cables and smell of burnt cable. Didnt paid attention at that time.

Purchased a new 150 euros Unibat AGM 30AH battery. Took it on and and i realise that the clock is off before putting the key in the ignition switch. GPI cables still free running, stripped.

At that time i have posted here the clock problem and with your help i found out that the green plug behind the instrument cluster was melted in pins 1 & 2. Played a bit with the plug only and managed to plug it properly on the instrument and clock was on again. Happy

I thought it was time to troubleshoot the issue with no starting engine with my new juicy powerful battery on bike.
Started the bike with half of turn of the start motor. Wow i said. It was the battery. problem solved.
With the bike on the center stand started it again after 5 minutes, everything ok. tried the same process 10 - 15 times over a weekends period. It was starting all the times and running great (on the center stand)

Monday morning taking the bike off the center stand to take it for a ride. 

Starter motor revving BUT engine could not start!!!! 

Back on the center stand. Lifted the tank to look for grounding problems on harness / frame etc. Everything in place some rust on the grounding terminal but not so major issue . 
before securing the tank back in place tried to fire it up. It started the engine !!! 

Tried several times. Starting ok. the had a flash idea to take it off the center stand. Did that and started ok again.
On the side stand , secured the tank in place. Tried to start it. No luck. 
What a headache. Unscrewed the tank cap and reached the fuel pump cables. Now it has a plug ( no original pump ). Pushed the plug a bit and realised that the pump is moving almost freely inside the tank  
Tried to start the bike and started ok. So it looks that something's loosing contact that is relevant with the fuel pump. ( I guess )

This is the situation now. So i decided to order a new original Fuel Pump, vibration damper and the plastic base. Also ordered a fuel sender ( old stick type one, used only ) and Motorworks offered to replace FOC the GPI switch.
I have a fully working instrument cluster (round pins 1988 K75RT ) and waiting for a green plug too from Dai member. 

By next week everything will be delivered, so i m going to proceed to GPI replacement myself since i cant trust the mechanic no more, will do some spline lubrication also and replace rear disc rotor (BREMBO) and pads since the one i have look like cracked in 2-3 spots and reasonably thickened out. 

Sorry for the extended text but i think its the only way to give you the rear state of the whole process.

It seems like the problem in the cluster have been there for a long time, but
getting worse over time (able to flow more current).

In picture #2 in post #1 and the picture in post #4 it looks like pin 1 & 2 is
missing.....does they?....or does it just look like it in the pictures?

How big (in A) is fuse #3 from the top?

Correct. Pins melted so they stuck on the instruments back shell when trying to remove it from the main cluster body.
The fuse is 15A.
After I fixed the clock issue by manipulating the melted green plug a bit to get the female pin one to align with male pin of the instrument I left it on bike since it's parked home.
By my mistake with the GPI cables towards the instrument stripped and left close to the frame I have mounted the side panel back in place. Then I noticed that the clock went blank again. Checked the 3rd fuse and it was blown for first time.

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Just leave the fuse out, or the short in the cluster gonna drain your battery
........which I'll guess have happened plenty of times already.

Cluster is already out , new one came in have to do some mods from the old to the new one though before installation ( fuel sender PCB) and battery poles disconnected

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Has the new plug arrived yet?

Not yet Dai. Guess in a few.days will be arriving

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Times like this you feel great about being member of a community like this.
Thank you Dai for the gift!!



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You're more than welcome. It and its mate would just have sat in the miscellaneous connectors drawer doing nothing.

Upper photo my original instrument 1985
Lower photo a K75rt with stamp 1988 on the rear


Detail from the "new"


Detail from the original (guess this are not original solderings..)


Inge could this be the problem?
I ' m swapping PCB s today for the 7L - 4L lamps since my early K had the early fuel sender ( electronic one )

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The two last pictures shows the connections for the stepper motor which
drives the odometer (and trip odometer).
On your "new" instrument the wires is connected to the side terminals
instead of the top terminals as in your old instrument.

Οκ. Got that.

So this is the old PCB for the sender.
By carefully inspecting it I notice that the old PCB has 3 terminals Vs 2 terminals lower side on the new instrument and 2 Vs 1 terminals on the top side

Can I do the swap? Leaving two pins on the air?



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Later models doesn't have the 7 liter warning lamp, so from now on you
will only have the 4 liter warning lamp functional.
Have a look at post # 6 & 13.

Your "new" instrument is from a ABS model, remove the bulb for the ABS
warning....your 7 liter sensor gonna be directly connected to that bulb....
could be that the sensor don't appreciate the different resistance.

I see . Thank you.
If I leave the new instrument as is, I mean without swapping the PCB with older one what will happen? I won't even have the 4L light warning?
I read somewhere about a potentiometer installation so I could tube the 4L to come on at 7L .
Do you think this could be possible?

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George_Pap wrote:If I leave the new instrument as is, I mean without swapping the PCB with older one what will happen? I won't even have the 4L light warning?

The sensors is quite different...so yes no warning lamps would function.

George_Pap wrote: I read somewhere about a potentiometer installation so I could tube the 4L to come on at 7L .
Do you think this could be possible?

The sensors sits on a fixed heigth inside the tank....the potmeters on the PCB
is the current limiter for the self heating of the thermistors...changes the
sensitivety slightly.

What's wrong with a warning on 4 liter? Later models have a warning on 5 liter.

-------------------------------------------------------------------------------------
I also see that your old fuel level PCB is for a 7 screw housing, and the
speedometer in your old housing is for 9 screw housing.
So one of them have been changed earlier (I'll guess the fuel level PCB)
How many screws is it on the rearside of your old housing?

Inge K. wrote:

-------------------------------------------------------------------------------------
I also see that your old fuel level PCB is for a 7 screw housing, and the
speedometer in your old housing is for 9 screw housing.
So one of them have been changed earlier (I'll guess the fuel level PCB)
How many screws is it on the rearside of your old housing?

I dont have it in front of me right now but i m pretty sure that the older housing has 2 screws less than the new one!

Then it seems like it would easier to do as mentioned earlier in this thread
to swap the blue conductive film (and the related plastic).

Else you must mod the fuel level pcb to make space for the extra screw
and drill a new hole for the repositioned mounting screw.

Oops.. I thought I should just replace the PCB as I did.

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As you did get a complete instrument instead the blue conductive foil only,
I was assuming that you rather wanted to use the "new" complete instrument
sorry, my fault .

Also then I didn't remember about the 7/9 screw differences, so it did look
like a easy task.

Maybe I confused you. I did used the new instrument cluster . I just took the fuel sender PCB only from the old one.
Is this ok?
As for the missing hole due to more screws of the newer instrument I just cut / lowered the specific female plastic screw insert so it will be installed minus one screw.

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Should function OK....fill the hole where the screw is missing.
Did you remove the ABS warning bulb as mentioned in a earlier post?

Yup! I did. My only worry is that with less than half a liter of fuel in the tank red light is still off. It's got late though and did not open the instrument to check for bulb etc.

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Sorry to hear that...if it did function as normal earlier, I have no other
suggestion than measure the conductivety between the connections
in the circuit...signal in from the tank sensor is at pin 7.

Inge K. wrote:Sorry to hear that...if it did function as normal earlier, I have no other
suggestion than measure the conductivety between the connections
in the circuit...signal in from the tank sensor is at pin 7.

Will check carefully

Thanks once more!