Help!!! Servo Brakes

martincito · 01:23 PM

I'm in the south of Patagonia 400 miles away from Ushuaia, the goal of my trip, and the servo brakes in my GS stopped working this morning.

When I start the bike the brake failure light blinks four times per second and stays that way. The servo is not working and I have to push the lever quite hard to stop the bike.
If I start the bike many times sometimes the servo works but ussualy it doesn't.
What can do?
Thanks for your help

signit98 · 02-16-2009, 01:25 PM

Check the handguard and see whether it moved and touches the lever. If the lever is pressed in even slightly, the brakes will go into error mode, Martin.

Make sure the lever is free and can be moved forward form the neutral position. That is in 99% of the time, the problem...

martincito · 02-16-2009, 01:38 PM

The hanguard is not touching the lever. Sometimes when the servo engages stay on (I can hear that high pitch sound) even when I release the lever.

signit98 · 02-16-2009, 01:53 PM

Ok, next check the rear lever and make sure there is no interference from that end. Unfortunately, if that is not the case, the problem is within the servo unit.

That might be a bit of a problem, depending where you are... try disconnecting the battery for about 30 minutes and see whether it resets.

The one thing you can do to regain full brakes as a temporary fix is to exclude the servo and hook up the brakes DIRECTLY to the master cylinders. That way you won't have ABS but you will have full brake pressure... I imagine that brake lines are easier to fin where you are than a ABS/Servo Unit.

SergioK · 02-16-2009, 02:46 PM

Ralf, does an ABS sensor gap error or broken abs sensor wire make it flash at that rate?

AndrewA · 04:09 PM

Look for the simple stuff first.

Is it possible that you've lost some brake fluid? If you can pull the tank off you should be able to check pretty easily. If the fluid level is low, you should hear the whiring every time you pull the lever.
You can check and bleed the brakes with no special tools (other than a turkey baster).

Get your voltage checked as well. This can also cause servo failure.

Does the rear work?

edit:

Quote:

Originally Posted by martincito

The hanguard is not touching the lever. Sometimes when the servo engages stay on (I can hear that high pitch sound) even when I release the lever.

Try jiggling the front brake lever if that happens again. Look to see if the rear brake light stays on - This same thing happened to my GS - I thought that I had a faulty handlebar switch - it turned out that I just needed to tighten the lever.

AndrewA · 02-16-2009, 03:58 PM

Here's a good guide: http://advwisdom.hogranch.com/Wisdom/service_abs3.pdf

martincito · 02-16-2009, 04:15 PM

Now the brakes are working better. I think there is two things causing problems.
One is something with the lever. If I shake the lever back and forward up and down
the servo engages and also I have to do that to stop the noise.
And the other thing could be low battery voltage. The failure started after riding on cold rain with the fogs lamps and heat grips on.
At least now the servo is on. Enough to get me to Ushuaia.
Many thanks for your help!

signit98 · 02-16-2009, 06:59 PM

I didn't go to the empty battery, as I considered that you are riding the living daylight out of that thing... but yes, that could VERY WELL be a problem. If the lever is loose, that could be an issue but you did not mention that either... good points, Andrew. As is the fluid level... but you should notice a drop on the handlebar reservoir as well, if you have - in fact - lost fluid.

See if it gets better again with a fully charged battery... is so, you'll just have to manage the load/draw a little better... if you know the problem, it's easy to avoid. Good luck and just keep having fun.

I am, btw., installing a second battery for my ride up north... another reason why I was looking for a sans-ABS bike... the space that is normally occupied by the ABS Pump is perfect for a second battery.

AndrewA · 02-16-2009, 08:10 PM

Quote:

Originally Posted by martincito

Now the brakes are working better. I think there is two things causing problems.
One is something with the lever. If I shake the lever back and forward up and down
the servo engages and also I have to do that to stop the noise.
And the other thing could be low battery voltage. The failure started after riding on cold rain with the fogs lamps and heat grips on.
At least now the servo is on. Enough to get me to Ushuaia.
Many thanks for your help!

Excellent.

Try tightening no. 7 and 9 in the drawing below.
On my bike, even though the bolt felt tight, I tightened it just a little tighter than I normally would have, and the problem stopped immediately and hasn't come back since.

AndrewA · 02-16-2009, 08:15 PM

Quote:

Originally Posted by signit98

I am, btw., installing a second battery for my ride up north... another reason why I was looking for a sans-ABS bike... the space that is normally occupied by the ABS Pump is perfect for a second battery.

Are you going to use a switch like a boat (Batt. 1 / both / Batt. 2)?
Why not just stuff it in a top case?

signit98 · 02-16-2009, 08:30 PM

I'll try to keep the weight as low on the bike as I can... a battery in the top case would be to top-heavy... and then, I don't want to have to deal with the whole connect/disconnect thingy...
I do have the space ON the bike, why not use it? I'll need ALL the space I can find alongside and on top of the bike for all the other stuff I am taking

Yeah, either a boat like switch or a solenoid... Still working on that... Boat switch is very big.

PFFOG · 02-17-2009, 08:08 AM

When I was in Europe we had two, 2007 1200 GS's do the same thing, and both were attributed to the rear brake lever return spring getting weak and not fully returning the lever.

Push the lever down with your hand and see that it returns with authority and is firmly seated against the stop.

I did a quick barnyard repair on the bikes by sliding a standard 8mm nut over the hook on the spring under the lever. It added enough tension to fully seat the lever