BMW K bikes (Bricks)

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1Back to top Go down   Couple of electric questions Empty Couple of electric questions Mon Mar 14, 2022 11:10 am


New member
New member
Hi all!

This is my first post on the forum, so please forgive me if the formatting is a bit wonky. English is also my second language, so some sentences may not be so clear.

I am currently building a cafe racer/scrambler 1987 BMW K100 RS. I'm rebuilding the bike at the moment, but I am having some trouble with my electrics. I have 3 questions/situations that I would like to get some help with:

1. Turn indicators

I have installed these LED turn indicators on my bike. I am having a similar problem as described on this post, the indicators only light up and a beeping sound is heard. No flashing at all. Do you think that my problems would be fixed by removing the ground on pin 7 of the U243B integrated circuit as described in the reply by robmack or should I start looking for the correct resistors for these indicators?

2. Tail/brake light
I have installed this LED brake/tail-light on the bike. I am having some issues with this. I have located the correct wires for brake/tail lights on the main wire harness of the bike and tried plugging them in accordingly (1 wire for the tail light, 1 for brake light and 1 ground). I have come across different situations with the light
  1. All 3 wires plugged in - The tail light does not work, but if I press the brake light switch (turn on the brake light), the tail light lights up. This light that comes on is not the brake light, as I have seen that it is brighter. So in summary, tail light does not work but lights up when I press the switch.
  2. Only plugging in the brake light wire - The tail light does not work. The brake light lights up normally (brighter than in 1.) when pressing the switch.
  3. Only plugging in the tail light wire - The tail light works normally. The brake light does not work at all. 

So currently the situation is that whenever I plug in the brake light wire, the tail light stops working and only lights up when pressing the brake light switch. I have tested the light using a battery (plugging the tail light and the brake light wire directly to a battery), the light works fine. Any ideas regarding this? Do I need a resistor or do I need to modify the BMU somehow?

3. Speedometer Acewell 2853
I have installed my speedometer succesfully otherwise, but I am unsure about the placement of the yellow wire (speed). I am using the Marulabs BEP 3.0 lunchbox remover. Should I just plug the yellow wire in to the SPD-slot on the BEP box? The yellow wire is forked in to two, but I think I only need to plug in one wire to the box?

I will happily provide any extra information needed about these problems and I really appreciate anyone taking the time to read through my post.

Thank you for reading, looking forward to your insight!




2Back to top Go down   Couple of electric questions Empty Re: Couple of electric questions Thu Mar 17, 2022 6:47 am


Silver member
Silver member
The blinker and tail lamp controls work on the power consumption detection. The LEDs require too low amperages for those systems to behave normally.

Revert to normal lamps or add resistors in parallel.


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