ST1100 LBS (linked braking system) failure

[davowolf]

My local bike technician (not Honda specialist) tells me that whilst the hand brake lever is operating front+rear as normal for LBS, the footbrake is only operating the back brake - not the front. That is where his and my knowledge stops. Can anyone advise what the porblem might be? I am continuing to ride - the brakes otherwise have been overhauled.

 

[chokozip]

My understaning of the LBS is it works when in motion.
Did your tech check this in motion or sitting on the stand?

Sean:biker:

 

[Firstpeke]

The secondary master cylinder only applies pressure to the rear outer pistons when the bike is moving and the left front caliper moves under braking (2000 model).
When stationary no pressure will be applied to the rear only the front outers.

Similarly when applying the rear brake, only the rear inner piston initially and after a slight delay the inner front pistons, irrespective of motion.
When moving the SMC comes into play due to the effect of the center pistons being activated on the front and hence the rear outers.

So when stationary if using the front brake lever, only the outer pistons on the front are activated.
When stationary using the rear pedal actuates the rear center and after a short delay, both front center pistons.

When moving using the front brake actuates the outer pistons on the front, subsequent motion of the left front caliper actuates the SMC and hence the two outer pistons on the rear.
When moving using the rear pedal activates the rear center piston and after a very small delay actuates the two center pistons on the front, subsequent movement of the left front caliper actuates the SMC and hence the two outer pistons on the rear caliper.

As I say this is for my 2000 model ABS/CBS/TCS bike, earlier ABS systems may be different.

 

[Blrfl]

If your mechanic isn't very familiar with LBS, he may have failed to bleed the secondary path into the front caliper, leaving air in that part of the system. That would dead-end any pressure coming from the rear master cylinder. Not bleeding the system in the right order might also cause similar problems.

I'd stay off the bike until you find out how the system was bled, because if there is air left it it and it migrates, you could come up short on brakes at some point when you really need it.

From Firstpeke's description and what I was able to glean from the service manual, LBS on the 1100 is very similar to that on the 1300, in which case this diagram might be useful: CLICKY

--Mark

 

[George]

Mark has it right, Dave. Bleeding sequence is important. Any air between the rear master and the front calipers may defeat the Delay Valve.

Correct bleed sequence for Your 99, FirstPeke's 2000, and my 2001 are all the same. ABS II. Here 'tis, per the 2001 shop manual:

Lever (front) brake line
Open top bleed valve on either side and bleed. (I use a Mity Vac.)
Open top bleed valve on other side and bleed.

Pedal (rear) brake line (here's where sequence gets important)
Left front caliper lower bleed valve
Right front caliper lower bleed valve
Rear caliper front bleed valve
Rear caliper rear bleed valve

(Suck a bunch of fluid thru all the lines. Book says 1/2 liter total in the system!)

If that don't solve your problem, suspect the Delay Valve (not the PCV, Proportional Control Valve. I had it wrong in my PM back to you.)

Phil's diagram is correct:

The Delay Valve is the unlabeled component at the upper-left, between the Rear Master and the front calipers.

The PCV is between the SCM (Secondary Master Cylinder) and the Rear Modulator.

Given that your rear center operates correctly, but the front centers do not, eleminates the rear master cylinder.

In your postion, I'd first do another complete bleed, following the steps listed above.

Keep us poSTed.

 

[davowolf]

Thanks y'all especially Firstpeke, George and Blrfl for this. I've printed it off and given it all to the tech at my local bike shop and today given them the bike back to initially do the bleed job, in the correct sequence. Lets see if that fixes it. Notwithstanding Eric's doubt (on my-mc) that the problem exists at all. Now that's worrying....

Just to compound the problem an additional problem has occurred since they handed it back after last Saturday; ie on a nice smooth downhill road (not many of them after the winter snow we've endured in the UK for the last month) pressure on the foot pedal makes the bike a bit 'lumpy' or slightly judder, as if the ABS is trying to kick in under normal breaking conditions.

Could this be that the gap with the castellated wheel has been set wrong ? Remember, the rear pads were all changed last w/e + a new disc (?? ouch...) and this gap would need to have been re-set.

So lets hope that 2 simple solutions get the bike back normal.

 

[wjbertrand]

The secondary master cylinder only applies pressure to the rear outer pistons when the bike is moving and the left front caliper moves under braking (2000 model).
When stationary no pressure will be applied to the rear only the front outers.

Similarly when applying the rear brake, only the rear inner piston initially and after a slight delay the inner front pistons, irrespective of motion.
When moving the SMC comes into play due to the effect of the center pistons being activated on the front and hence the rear outers.

So when stationary if using the front brake lever, only the outer pistons on the front are activated.
When stationary using the rear pedal actuates the rear center and after a short delay, both front center pistons.

When moving using the front brake actuates the outer pistons on the front, subsequent motion of the left front caliper actuates the SMC and hence the two outer pistons on the rear.
When moving using the rear pedal activates the rear center piston and after a very small delay actuates the two center pistons on the front, subsequent movement of the left front caliper actuates the SMC and hence the two outer pistons on the rear caliper.

As I say this is for my 2000 model ABS/CBS/TCS bike, earlier ABS systems may be different.

This description is correct and quite clear but the OP seems to describe the opposite problem. Assuming the bike was stationary, why was pressure applied to the rear brake when using the front lever? That should not happen unless the bike is moving.

If the bike was underway during the test how did the tech know that rear caliper pressure was being applied when the front lever was activated or that no braking pressure was sent to the front when activating the pedal? Do they have a way of testing this whilst riding the bike?

 

[Blrfl]

...pressure on the foot pedal makes the bike a bit 'lumpy' or slightly judder, as if the ABS is trying to kick in under normal breaking conditions.

Could this be that the gap with the castellated wheel has been set wrong ? Remember, the rear pads were all changed last w/e + a new disc (?? ouch...) and this gap would need to have been re-set.

I don't know enough about how the ABS computer on the 1100 behaves, but if one the sensor in one wheel isn't providing consistent pulses during the start-up diagnostics, you should get a warning about it. If you have the tool kit that came with the bike, there should be a 0.5mm feeler that you can use to check the gap yourself in about five minutes. Make sure you check it in several places, and visually check that the wheel is positioned laterally directly under the sensor.

A few years ago, there were a couple of people who took delivery of 1300s that had similar problems which were a result of the front wheel being improperly installed. On that bike, there are spacers that are different sizes which have to be in a specific spot or the wheel doesn't line up properly. If your front wheel was off, that might be worth investigating. From looking at the fiche, that may not be it since the speedo gear housing appears to serve the spacer function on the left side.

HTH.

--Mark

 

[davowolf]

Mark can't check the gap myself till I get the bike back - probably Saturday - by which time it may have been fixed. As regards the checking whilst underway, I imagine they did it on the wheelie roller treadmill thingie used to check brakes for the annual UK MOT test - you must have that kit over there - its like going nowhere fast ....just like these little blighters ...

 

[George]

Good luck on the process, keep us poSTed.

 

[broc11]

Thanks for posting this George,I finally understand the linked system now

 

[satish]

Mark can't check the gap myself till I get the bike back - probably Saturday - by which time it may have been fixed. As regards the checking whilst underway, I imagine they did it on the wheelie roller treadmill thingie used to check brakes for the annual UK MOT test - you must have that kit over there - its like going nowhere fast ....just like these little blighters ...

i am faceing some issues brake system with honda st1100AY 2000 model. can you send electrical drownings

 

[Larry Fine]

Satish, welcome to the forum.

You should ask your questions here, and include more information: https://www.st-owners.com/forums/forums/st1100-brakes.475/post-thread

 

[satish]

Satish, welcome to the forum.

You should ask your questions here, and include more information: https://www.st-owners.com/forums/forums/st1100-brakes.475/post-thread

thanks