I have a '90 K100LT.  The ABS has never worked since I got the thing.  Was out for a bit of trip today and decided to do something about the annoying blinking lights and having to push the ABS switch every so often.  So did a little research and pulled the 2 blue relays in the electrical components box.  So the blinking has thankfully stopped and the ABS light in the speedo is now out, but the warning light remains on steady.  The brake light bulb is fine.  I have a vague recollection of the BMU on my '85 K100RT flaking out and I had to jumper around it.  Is this what I'm looking at here, or is there something easy I'm missing?

Thanks,
Steve

Hi,  

The pin #8 of ABS ECU connector and the pin K on the BMU are connected in parallel and the same K controls the bulb monitor lamp.

if the BMU is OK then ABS ECU is doing bad so cut the white/blue wire at the ABS connector pin #8. 
it will bring the things fine.

I know what you mean, that light will drive me crazy too, especially at nigh. I ended up fixing the ABS and for a couple years it only kicked in when I made it just to test it. Well one time in the rain, a panic stop and I grabbed to much front brake and the ABS kicked in and I believe it kept me from going down. You may think about trying to fix it. Mine was easy I just had to replace the rear speed sensor, adjust and clean up connectors, then about 20 exempt to clear the codes before the "brain" decided to work.

I'd agree with Caveman. Worth attempting to fix. ABS has saved me a few times now.
Start by checking the fault codes. That should lead you to a possible remedy.

http://www.largiader.com/abs/absfault.html

As you have removed the blue relays you will still have the abs light on.  To stop this just unplug the ABS control under the seat.  I put the multiplug in a plastic badg to keep it safe and dry. I left the unit in place until I realised it lives in a nice place for my too roll.  
By unplugging the ABS Multi plug your light will go out and the BMU will function as it should unless you have a separate fault on that circuit.

Folks, thanks for the comments.  I pulled the harness connector off the ABS brain, and the warning light did indeed go off after working front & rear brakes.  It is SO nice to not have any warning lights on after putting up with it for a few riding seasons!

Re: fixing the ABS - yeah, I'd like to sometime - but mostly because I like stuff that's supposed to work - to actually work.  I've had ~50 different bikes in my riding career, and yet to have ABS on any bike.  So I just haven't been able to prioritize it as essential functionality.  I'll certainly never argue that it isn't a good thing to have, but the bike is just one of several that shares riding time during a fairly short riding season and putting up with the warning lights has been a lot more bothersome to me than not having ABS so far.

Thanks again!
Steve