Brake servo loss

[harveyrawn]

I was riding a twisty road yesterday with occasional use of my R's brakes at turns. Suddenly, the red triangle warning light came on, the ABS light started flashing on its fast cycle, and I had no servo-assisted brakes front or rear. The residual manual brakes worked, sort of, and I continued home in that mode. At home, I turned the ignition off, then back on, and servo operation seemed to resume normally. So maybe the problem was some electrical gremlin?

All the bike's systems seemed to be in order. Aside from adding a new Odyssey battery recently, the only other recent electrical event was adding a Kisan Signalminder SM-5 including the connection to the brake wiring that pauses the turn signal countdown when the brakes are applied. The only plausible theory I have at the moment for the servo problem is that the Signalminder's connection to the brake circuit somehow created a fault in the ABS system that led to the servo (and possibly) brake failure.

Does that seem feasible?

[llahbocaj]

I can't speak to the feasibility of the signalminder causing your servo fault, I thought that these faults were limited to the realm of the ABS pump and its sensors but I had a similar problem on my 2004 RR around 12k...

On starting the bike sometimes ABS would come up and sometimes it would not. Sometimes it would not come up but later on it would suddenly start working for no apparent reason mid-ride, or conversely...stop working. Imagine grabbing your brakes expecting no servo assist...only to find that they had come back on and you have significantly more braking power. It was an intermittent sensor on the rear brake pedal. It spit a code to the diagnostic if you have a friend with a GS911. I had to take it in to a dealer near where I was traveling through, it was probably $200 for the new sensor but certainly worth it to know what kind of brakes I was going to have the next time I grabbed them.

[harveyrawn]

On starting the bike sometimes ABS would come up and sometimes it would not. Sometimes it would not come up but later on it would suddenly start working for no apparent reason mid-ride, or conversely...stop working. Imagine grabbing your brakes expecting no servo assist...only to find that they had come back on and you have significantly more braking power. It was an intermittent sensor on the rear brake pedal.

That's food for thought and raises other questions. Does the rear brake pedal on your 2004 R only operate the rear brakes as my 2002 does and did the faulty sensor on the rear brake pedal disable servo operation when you only applied your front brakes?

[bimrluvr]

Hi Harvey,

Sorry to hear about your ABS glitch. The '04 has partially integrated EVO brakes which are different from the '02, but not dramatically. The brake pedal activates rear only...the front brake lever applies full front and partial rear.

It's also possible that a bit of dirt has mucked up your sensor/s. Try giving them a rinse with water or brake cleaner first and see if they cycle off/on properly again.

regards,

Mort

[harveyrawn]

Thanks, Mort.

I'll clean the ABS sensors and see if the problem repeats.

I thought that the ABS system could fail in a way where the servos continued to assist stopping, but ABS assistance was not available. Is that incorrect?

[bimrluvr]

You're probably correct. But I seem to recall a time I had when the ABS would not engage and neither would the servo. Surprised the hell out of me. Turned out my sensors were dirty. Only happened once though and that was 4 years and 40k miles ago.

[harveyrawn]

I had a one-time event shortly after I bought the bike two years ago. I rode to Big Sur on a Saturday in the rain and shortly after a hard downpour, the ABS light started flashing slowly but the servos continued working. Camped overnight and rode home on Sunday with the same brake setup. The next time I took it out, all systems were normal and the condition never appeared again. Maybe another case of dirty sensors.

[BoxerSteve]

I'm glad my bike doesn't have ABS. Nice and simple, easy to service yourself, reliable braking. I guess I might be a luddite but I've never been a big fan of ABS.

[Ol' Jeffers]

+1 I don't like ABS on a bike. S'OK in the car but on a bike it seems to erode the skills
of riding and as it goes wrong I'd prefer not to rely on it!
Hope you get yours sorted out though, Harvey.

[harveyrawn]

This is the first bike I've owned with ABS and I've never used it. Glad it's there if needed, I guess.

[harveyrawn]

I cleaned the sensors with brake fluid and water and took it for a ride. Same result. Then charged the battery. Took it 80 miles today with all systems working normally. One or both of those procedures cured the gremlin.

[bimrluvr]

Hmmm. More likely the battery (unless it was still wet after the wash). Low voltage does funny things to the ABS and other systems. If it happens again after the bike's been sitting for more than a few days or a week, then it's almost definitely the battery.

[harveyrawn]

It was still wet for the first ride, then dried and charged for the second one. It's a newish Odyssey battery, so, unless the bike's charging system has some unknown defect, I tend to think it was some problem with the sensors. The strangest aspect of the episode is that the problem arose in dry weather after I had ridden about 60 miles.

[firedfromthecircus]

I believe this is becoming a common problem on 1150's of a certain vintage.
More information in this thread.
http://www.bmbikes.org.uk/Forum/viewtop ... 14&t=10921
Worth reading through I think.

The worst of it is as llahbocaj says, if you are riding with residual braking when suddenly your servo kicks back in again.............
Well, it isn't a nice thought.