intermittent electrical problem K75

Has anyone had this problem and what is the fix? Bike runs normal then instrument lights dim and dies. Won't start. Pull off road and try one more time. Instrument lights get bright and fires up and runs great. Runs great and then a day or two does the same thing again. Runs great for a while then does it again. So far it always has started back up after pulling off road. I priced ignition control unit $1100. I don't want to start guessing on expensive fixes. Please help.

Welcome to the forum! Hang on...I'm sure you'll get some good options from some of the K-Bike owners.

That sounds like a poor connection. Maybe a ground connection. First disconnect and clean the connections at the battery. Even hidden corrosion here can vary resistance with temperature and humidity which can cause the erratic results. Also, on the frame backbone under the fuel tank you will find a cluster of brown wires connected to the frame. These are various ground leads. Clean this entire system of grounds. Also check that the negative battery cable is clean and secure where it connects to the side of the transmission.

The ignition control unit would not impact dimming lights or engine cranking. It is not a real candidate for this problem.

Hi
I went through this exact same problem with my 1990 K75 RT
Several people in the know advised me it was a dirty ignition switch.
They were right.
I took it apart, cleaned it and reassembled the switch and it fixed your problem.
There's a pictorial link out there on how to do it.
I had a hard time reassembling the switch until I did it with the switch upside down, then it went together.
I bet this is your problem.
I'll try and find the thread I had going on this site about it.
Best Regards

Last year my 92 K75S with ABS died at a stoplight in the middle of a ride. No warnings, just died and would not re-start, no juice to lights or starter.

I had the bike transported home and began investigating. The battery had failed (it was an Odyssey PC-680 more than 5 years old). I also installed a new voltage regulator (already had) in addition to a new battery.

The bike started just fine, but I had issues with the ABS light flashing. Using the ABS reset button failed to cure the flashing ABS light - I was about ready to resort to the tape cure (place a small piece of black or otherwise opaque tape over the flashing light ).

But I found some on-line instructions on the method for clearing the ABS. It involves use of a small bit of wire to briefly ground the middle contact in the three-conductor plug. More complete instructions are found here -
https://ibmwr.org/index.php/1998/04/01/abs-fault-clearing/

ABS diagnostic hints are found here -
https://ibmwr.org/index.php/1998/09/01/abs-diagnostics/

Other K-bike tech articles are found here -
https://ibmwr.org/index.php/k-bike-tech-articles/

A link to an aforementioned thread on K75 electrical issues is here -
https://forums.bmwmoa.org/showthread.php?94841-1990-K75RT-Electrical-problem

7194 said:

Has anyone had this problem and what is the fix? Bike runs normal then instrument lights dim and dies. Won't start. Pull off road and try one more time. Instrument lights get bright and fires up and runs great. Runs great and then a day or two does the same thing again. Runs great for a while then does it again. So far it always has started back up after pulling off road. I priced ignition control unit $1100. I don't want to start guessing on expensive fixes. Please help.

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Based on your symptoms, I would, in the order of ease to do, clean your kill switch contacts, clean your starter commutator, clean your ignition switch contacts. Odds are the problem is either your ignition switch or your starter.

https://forums.bmwmoa.org/showthread.php?92550-Cleaning-Replacing-Start-Kill-Switch

https://forums.bmwmoa.org/showthread.php?53377-Starter-Motor-overhaul-on-a-1992-BMW-K75S
Use Scotchbrite to clean the commutator.


https://forums.bmwmoa.org/showthread.php?85331-Ignition-Switch-Cleaning

how to dissassemble ig. swith

OK guys I got the ignition switch out and outer cap off I can't figure out how to disassemble it to get to the contacts. Afraid to pry and break something.. Does anyone know the trick to getting it disassembled? Thanks.

7194 said:

OK guys I got the ignition switch out and outer cap off I can't figure out how to disassemble it to get to the contacts. Afraid to pry and break something.. Does anyone know the trick to getting it disassembled? Thanks.

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Did you read the last link in my previous post that gives a step by step procedure with photos on how to disassemble the ignition switch?

ignition switch disassembled

Thankyou 98lee got the ignition switch disassembled and cleaned Couldn't have done it without your instructions

7194 said:

Thankyou 98lee got the ignition switch disassembled and cleaned Couldn't have done it without your instructions

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Those instructions were graciously provided by Don Eilenberger and are located in the K-Bikes DIY/Tech Library which is located at the top of this (Flying Brick) section of the forum.


Now, to complete this process, we hope you wil update us so we can know if that was the solution or if there still is a problem. That way we all learn.

ignition switch was the problem

7194 said:

Thankyou 98lee got the ignition switch disassembled and cleaned Couldn't have done it without your instructions

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after several rides and one long one out of town the bike has had NO problems. Thanks again for all the good info:

7194
Glad you got it fixed.
That is one odd problem that ign switch cleaning fixing those shutoff's
When I took mine apart to fix that problem it looked Very Clean inside, no residue, black stuff etc.
Cleaned it with a eraser and fixed my bike.

7194 said:

after several rides and one long one out of town the bike has had NO problems. Thanks again for all the good info:

Click to expand...