1991 K75s with ABS front brake issues

[natejaeg94585]

I recently bought this bike, and it's got some problems with the front brake, as in it doesn't have one. I attempted to do a reverse bleed and it seems like there is a clog somewhere in the system. I purchased some new lines from Motobins and am just waiting on them to get here. When you pull the brake lever it goes all the way back to the grip which in my past experience tells me that the master might also need to be replaced, or rebuilt. Is there a place that sells a rebuild kit for it that you would trust enough to recommend?
Is it possible that this is an ABS issue?

 

[88bmwjeff]

Euro Motoelectrics is a good place to get parts. They are a top-notch company and delivery is very quick.

Euro Motoelectrics

 

[lee]

Maybe @98lee can help with that information.

 

[natejaeg94585]

So the good news is, that after removing the brake master, unclogging it, replacing the O-ring between the reservoir and the master, and replacing the front brake line, then spending 2 days bleeding it the front brake works. Now I need to figure out the ABS light, and the warning light. I love working on things, but brakes are never fun. I am still waiting on a proper rebuild kit for the master to come in to properly ride the bike.

 

[pauls1150]

ABS/Warning lights: table attached;
additionally:
Gen AND ABS flashing alternately at 1Hz = Fluid level in Integral ABS too low, Low voltage

 

[RANBUSH]

When I had a '94 K75S and the ABS died, I put a piece of black tape over the ABS light.

 

[natejaeg94585]

ABS/Warning lights: table attached;
additionally:
Gen AND ABS flashing alternately at 1Hz = Fluid level in Integral ABS too low, Low voltage

The only thing I dont see in the attachment is what I have. Both ABS, and the general warning light is on solid. I will attempt to do a reset on the ABS to see if that gets that one taken care of at least.

 

[98lee]

Nate,

Sounds like you haven’t cleared the bulb monitor function yet. After turning on the bike, it goes through a rear bulb check function, checking the brake light, taillight, front brake light switch, and rear brake light switch. You need to apply the front brakes, release , and then the rear brakes and the release. IF both brake switches AND both the taillight AND the brake light are operating, THEN the lights go into ABS mode. After the bike gets up over 10 mph it runs the ABS checklist.

 

[98lee]

ABS/Warning lights: table attached;
additionally:
Gen AND ABS flashing alternately at 1Hz = Fluid level in Integral ABS too low, Low voltage

That table is for later ABS, not the first Gen. that K75s have. There is no low fluid light on K75 ABS.

So the good news is, that after removing the brake master, unclogging it, replacing the O-ring between the reservoir and the master, and replacing the front brake line, then spending 2 days bleeding it the front brake works. Now I need to figure out the ABS light, and the warning light. I love working on things, but brakes are never fun. I am still waiting on a proper rebuild kit for the master to come in to properly ride the bike.

When you go to bleed the front brakes, turn the steering all the way to the left as you are bleeding. This gets the master cylinder so the high point is the lever end of the cylinder. If you try to bleed it with the steering straight ahead or to the right, the hose end of the master cylinder is the high point and you will trap air at that end just above where the hose goes into the master.


Nate,

I sent you a PM with my phone# (look at top bar forhighlight) I can talk you through any further issues.

 

[natejaeg94585]

That table is for later ABS, not the first Gen. that K75s have. There is no low fluid light on K75 ABS.

When you go to bleed the front brakes, turn the steering all the way to the left as you are bleeding. This gets the master cylinder so the high point is the lever end of the cylinder. If you try to bleed it with the steering straight ahead or to the right, the hose end of the master cylinder is the high point and you will trap air at that end just above where the hose goes into the master.


Nate,

I sent you a PM with my phone# (look at top bar forhighlight) I can talk you through any further issues.

Thank you for the information, and your number. Unfortunately my riding season has been cut short due to an accident at work. Once I can ride, and do more work to the bike, I will let you know if I run into any more issues.

 

[glenvine12]

Sorry to hear about the accident. You didn’t say if the ABS is functioning. I assume with the light show-litany, it is not.. But would be good to know. I bought a 1990 K1 in 1997 that had 917 miles on it. The brake fluid I could see looked good. The ABS light show was happening and the ABS did not work. The dealership I bought it from (not BMW) said the ignition key had been turned to the ON position with the battery disconnected and that disabled the ABS. They told me to go to a BMW dealer and have the fault cleared. I was dubious but I’d never had ABS so the bike stopped like any other bike I had to that point.

I went to a BMW dealer. Sure enough the fault light cleared and ABS function returned.

I’ve never had a wheel sensor go bad or be improperly rigged but that should be checked if all other fixes don’t work.

 

[98lee]

One of the most common causes of the ABS failure light coming on is the bike sitting until the battery gets lower than the ABS threshhold. The low battery trips a code in the ABS module. Charging or replacing the battery does not automatically reset the code in the ABS module. Reseting is a manual procedure that involves grounding a contact (in the appropriate order) to erase the code. If all else is good, the light will go out as you ride off. Takes about 5- 10 minutes.

 

[natejaeg94585]

One of the most common causes of the ABS failure light coming on is the bike sitting until the battery gets lower than the ABS threshhold. The low battery trips a code in the ABS module. Charging or replacing the battery does not automatically reset the code in the ABS module. Reseting is a manual procedure that involves grounding a contact (in the appropriate order) to erase the code. If all else is good, the light will go out as you ride off. Takes about 5- 10 minutes.

The battery voltage might actually be my issue. When I bought the bike it had been sitting for a while, and when I went to start it the other day, the battery was almost completely dead. I will try to get a tender on it and let it charge. Once its able to start I will also check the alternator voltage. I just cant wait to be able to ride again. The few times I have had the ability to ride its been a very comfortable ride.

 

[zagando]

When you go to bleed the front brakes, turn the steering all the way to the left as you are bleeding. This gets the master cylinder so the high point is the lever end of the cylinder. If you try to bleed it with the steering straight ahead or to the right, the hose end of the master cylinder is the high point and you will trap air at that end just above where the hose goes into the master.

Lee; I cannot thank you enough for posting the above tip! (Explanation to follow)

A few days ago I replaced my old bar risers with Voigt Moto Technik barbacks for a bit more height (now 30mm) and some setback (21mm) that I didn't have before. I also added a VMT 3cm brake hose extension which allowed the barbacks to function properly without having to replace the brake line and cables. I placed my order online on Wednesday afternoon here in Texas and the package from Deutschland arrived on Friday almost exactly 48 hours later (!)

Here are some pix:


Saturday I carefully removed the old risers and installed both the barbacks and brake hose extension, (which apparently could be installed without having to bleed the brakes in most cases).

I went ahead and got everything installed and then decided to replace at least some of the brake fluid which was at least a year old or more since I bought the bike last June. I removed the master cylinder cover and carefully siphoned bits of old fluid out with a turkey baster and into a container for disposal while topping up with fresh DOT4 I'd picked up at O'Reilly's earlier that day. Then I put the rubber insert back in, cleaned up some excess fluid and then the cover and screws went back on.






Then I performed the three full minutes of pumping the front brake lever and then let the bike sit for 12 hours with the clutch lever cable-tied to the left handlebar grip as per the VMT instructions. There was no braking action when I did the 3 minutes of lever action but figured I'd wait overnight to see if the clutch lever trick did pressurize the system as indicated.

Sunday afternoon came around and it was time to check things out...

No front brake at all, still!

I thought to myself I will have to rent a trailer and take the bike up to the nearest dealer in San Antonio (350-mile round trip) and drop it off for them to power bleed the ABS brake system (as the Clymer Manual dictates). I went to our local U-Haul site here in town which was closed but noted a motorcycle trailer in their yard, so that gave me a bit of hope. When I got back home I decided to read up on ABS brake bleeding here when I came across this thread with the "turn all the way to the left" trick.

I went into my garage and turned the bars and began pumping the front brake lever---and VOILA! I had brakes again!

Once I was really sure I had both front and rear brakes I took the bike out for a quick trip to my post office and back and everything was good---except I noticed a few drops of brake fluid seeping out at the base of the M/C. After a quick run to the kitchen to get some soapy water and paper towels I cleaned it off the lever housing, gas tank and fairing side as quickly as I could---and no worries, I caught it in time (I plan to strip the recently repainted red and black tank anyway and polish it to bare aluminum as I did with my previous K75S in Hawaii in 2009). I think the resevoir was slightly over-filled hence the seeping / leak that has now disappeared, and I'll continue to keep an eye on things further just in case---but for now I am a very happy Kamper thanks to Lee's brilliant tip!