1100 ABS rear brake questions

George

George

Joined
Feb 5, 2005
Messages
8,539
Age
77
Location
Kingman, Arizona
Bike
2000 ST1100 ABS TCS
STOC #
004
Removed and cleaned all parts on the rear brake caliper last night. Marginally better but still too much drag.

So, who is the resident 1100 ABS Guru???

Questions (given that the problem is not the rear caliper):

Any history of Secondary Master Cylinder (SMC) on the 1100 hanging up? Looks very similar to a rear master cylinder but also feels "stiff" when operated manually. Short throw?

Any hints/tips how to check the proportioning valves for correct action? I have no knowledge of these things

My current plan is to remove and closely inspect the SMC, where else do I need to look?

TIA for any/all responses.

One thing I noticed last night (surprised me to see the front brake operates two pistons on the rear while the rear pedal only operates the big center piston). As I was bleeding'em following reassembly, got a lot of dirty fluid from the front bleeder on the rear caliper despite having bled them last Thursday. Obviously didn't get all the old fluid out that time. Since the rear pedal also operates the front brakes, have to assume the SMC kicks in and operates those two outer pistons as well even if the front brake lever isn't touched so the rear system should be getting fully exercised each time either brake is applied.

BTW, I like the feel of the obviously stronger front end and brakes, once this little glitch is sorted, it's gonna be a good bike. Haven't kicked in the ABS yet tho. What can go wrong over time if this thing isn't really exercised?
 
George, as the bike has sat a while, I would suspect the rear master cylinder. I had a problem with the little return/relief hole blocking up on my '93 ABS bike (non-linked though). This is a very small orifice that relieves pressure from the caliper back to the master cylinder reservoir when the brakes are released. Simply rebuilding that cylinder won't solve the problem if that hole is blocked (don't ask). I ended up taking it all apart again and reaming out that little hole with some wire followed by a blast of brake cleaner.
 
Thanks, Jeff. I have new caliper seals and brake pads coming. Figure I'll do a full brake system rebuild then.

Waiting to get some proportioning valve info <fingers crossed>.
 
George said:
Thanks, Jeff. I have new caliper seals and brake pads coming. Figure I'll do a full brake system rebuild then.

Waiting to get some proportioning valve info <fingers crossed>.
Click to expand...

<edit> Oh, should add the rear fluid reservoir was almost empty when I first got her home, no rear brake at all at that time. Hmmmmmm.

Since the rear reservoir drives both the center-rear piston and center front pistons and the SMC... nah, I don't have it straight in my head yet...

BUT... a blockage in the rear master cylincer would cause pressure to stay on all three rear pistons cause that pressure passes _thru_ the SMC. Right?

<edit 2> I gotta go back and look at the colored diagram in tech forum. Heck, all I wanna do is go ride! :(
 
Last edited:
GEORGE - Here are some snippets that I have collected over the years on the ABS and the accompanying diagram -

The parts in red get direct pressure from the brake lever. The parts in green get direct pressure from the pedal. Either one causes some amount of front braking, which causes the SMC (yellow) to compress, sending pressure to the outer pistons on the rear.
Quote:
Originally Posted by ST13Fred
It appears the pedal operates all 3 center pistons. When the lever is activated, the pressure of the pads on the rotating left front rotor, moves the caliper up/fwd (the bike has to be motion for this rotation to happen), activating the SMC, which applies pressure to the outer rear pistons. This is what had me confused when the bike is static and I was getting no rear outer piston action.

Correct all the way around.

Quote:
So...........lever action operates ALL outer pistons (6). Pedal action operates ALL center pistons (3). If this is right, everything I've read over the years and now is wrong.

Mostly. Pedal action operates all three center pistons directly. Because the front centers cause some braking being applied to the front wheel, the SMC compresses and operates the outers on the rear as well.
The rear center is activated DIRECTLY via the pedal and the rear outers are activated INDIRECTLY via the pedal that is activating the SMC, by the DIRECT activation of the front left center piston !!!!!! Now talk about a confusing statement!!
 

Attachments

  • Linked Brakes.png
    Linked Brakes.png
    88.7 KB · Views: 449
Something's missing from that diagram, Phil. I know the SMC gets it's fluid from the rear reservoir but how? There's no bleeding process for it.

Also, nothing I've found explains the operation of the proportining valves.

Thanks for the help.

Oh, yeah, that diagram (looking at the SMC) appears to be for the 1300. Other than mechanical diffs, is the late 1100 the same?

Uncle Phil said:
GEORGE - Here are some snippets that I have collected over the years on the ABS and the accompanying diagram -

The parts in red get direct pressure from the brake lever. The parts in green get direct pressure from the pedal. Either one causes some amount of front braking, which causes the SMC (yellow) to compress, sending pressure to the outer pistons on the rear.
Quote:
Originally Posted by ST13Fred
It appears the pedal operates all 3 center pistons. When the lever is activated, the pressure of the pads on the rotating left front rotor, moves the caliper up/fwd (the bike has to be motion for this rotation to happen), activating the SMC, which applies pressure to the outer rear pistons. This is what had me confused when the bike is static and I was getting no rear outer piston action.

Correct all the way around.

Quote:
So...........lever action operates ALL outer pistons (6). Pedal action operates ALL center pistons (3). If this is right, everything I've read over the years and now is wrong.

Mostly. Pedal action operates all three center pistons directly. Because the front centers cause some braking being applied to the front wheel, the SMC compresses and operates the outers on the rear as well.
The rear center is activated DIRECTLY via the pedal and the rear outers are activated INDIRECTLY via the pedal that is activating the SMC, by the DIRECT activation of the front left center piston !!!!!! Now talk about a confusing statement!!
Click to expand...
 
GEORGE - Well, duh - didn't catch the ST1300 part! :eek:: Thanks for pointing that out. Since I plan on moving the brake system from an ABS over to my standard (not the electrical just the mechanical - already got the parts, forks, etc.), I've tried to gather up what I can for info. Norm has done a bunch of work on ABS pumps (I and II) and probably would be the best 'head' at this time.
 
Part of the of the confusion stems from the fact that Honda has apparently changed which pistons in which calipers are activated with which (lever or pedal) in different applications. George it seems your logic about a plugged return orifice also causing the fronts to drag makes perfect sense. As far as bleeding the SMC, On the ST1300 that's done at the PCV (proportioning control valve) but I don't think, not sure, the ST1100 LBS system has such a valve?

Could have sworn in the original LBS system, the pedal directly applied force to the outer pistons of the rear caliper and the inner ones of the fronts in order to maintain a rear bias. If that's true then the ST1100's system is plumbed differently than the 1300's
 
JEFF - Your scenario on the rear pedal is what I've heard from folks who are supposed to know. And I was thinking the reverse is true when you pull the front lever - middle rear, two outers on the fronts. But I could be wrong - already proved that! ;-)
 
Norm is the guy to ask. We are fortunate that he is a retired real mechanic that actually knows what he is talking about.

I haven't taken much notice of the ABS side of things as I have a standard, so can't say anything of use.
 
Uncle Phil said:
JEFF - Your scenario on the rear pedal is what I've heard from folks who are supposed to know. And I was thinking the reverse is true when you pull the front lever - middle rear, two outers on the fronts. But I could be wrong - already proved that! ;-)
Click to expand...

The ABS II on the 1100 is the same as shown on your diagram, Phil, but the SMC is physically different, same function. The outer pistons on the rear caliper are operated by the SMC.

Problem I'm having so far is how the SMC gets it's fluid. It's from the rear reservoir. None of the function diagrams show the route for the input of fluid, only output.

Reading chapter 23 in the service manual, looks like the Proportional Control Valve (PCV) between the SMC and the rear caliper could also be the problem. Pg 23-20 sez:

"As input pressure continues to increase, the cut piston activates, closing the valve and causing the output pressure to hold (Fig. B).

Pg. 23-18 shows all the hydraulic connection, just confirmed by actually looking at the bike: SMC gets its fluid from the rear reservoir and feeds fluid to the left front caliper center piston. Output of the SMC goes to the rear caliper out side pistons, so...

...bleeding the left center and rear outside pistons should flush those lines. Whew!

So, now I'm down to either the SMC or the PVC as the source of the drag.

STill thinking :think1:

None of this takes the ABS Modulators into account. Rear modulator is plumbed between the PCV and rear caliper so if one of those valves is stuck, could also be the problem. Since those valves (theoretically) don't activate unless the ABS operates, and flushing thru the lower bleed valve on the rear caliper shows no restriction, don't think that could be the problem.

Okay, Deba is up so I'm out to the garage to finish putting STick back together.

Those of you with an operational bike, please go ride and think of me. :( :D

Hmmmmmm, :think1:
 
ABS modulator problems are pretty rare. Besides that the ABS system runs a self check periodically (you can sometimes hear them cycle) so I expect any faults in the modulators would cause an ABS error code to be set and the trouble light to illuminate. I think I'd put the modulators last on the list as suspects.
 
wjbertrand said:
ABS modulator problems are pretty rare. Besides that the ABS system runs a self check periodically (you can sometimes hear them cycle) so I expect any faults in the modulators would cause an ABS error code to be set and the trouble light to illuminate. I think I'd put the modulators last on the list as suspects.
Click to expand...

I agree, Jeff.

Gotta take one back from my previous post, tho. Flushing thru the rear caliper, rear bleed valve probably does not flush the line between the SMC and rear modulator. Only way I can see to do that is to pump the SMC manually.

Any thoughts on that?

Or am I missing something simple? (probably :D)
 
I really wish I could help you George. I have frightfully little ABS experience as a practical matter, and my book is generation 1 stuff which doesn't match up with your bike at all....So, I am just trying to watch and learn just like everybody else.

How come we don't have a resident ABS II expert here??? Have they really been that trouble free???
 
BigTom said:
I really wish I could help you George. I have frightfully little ABS experience as a practical matter, and my book is generation 1 stuff which doesn't match up with your bike at all....So, I am just trying to watch and learn just like everybody else.

How come we don't have a resident ABS II expert here??? Have they really been that trouble free???
Click to expand...

I think by far most of the complications are related to the linked braking system and not the ABS per se.

George, on the ST1300 the SMC has to be positioned in a specific orientation, requiring the caliper bracket to be dismounted from the fork leg, and then brake fluid is drawn from the PCV valve using vacuum such as a miti-vac or similar. Maybe it's the same for the 1100? Does the 1100 have a bleed nipple on the PCV like the 13?
 
wjbertrand said:
I think by far most of the complications are related to the linked braking system and not the ABS per se.

George, on the ST1300 the SMC has to be positioned in a specific orientation, requiring the caliper bracket to be dismounted from the fork leg, and then brake fluid is drawn from the PCV valve using vacuum such as a miti-vac or similar. Maybe it's the same for the 1100? Does the 1100 have a bleed nipple on the PCV like the 13?
Click to expand...

Not mentioned in the procedure and not visible so I guess no. Maybe problems with the 1100 prompted the addition on the 1300? I agree the complications of the LBS are probably the source of most problems on the ABS II (from my limited experience.)

We do have a resident expert, Norm is here as well as at My-MC. He's reading all this now.

Hi, Norm. :D
 
Thanks for all the, John.

I have not replaced the pads.

I have disassembled and cleaned the rear caliper, it looked good before and better after. That helped marginally.

Applying the rear brake (center pistons on all three calipers) results in stuck pressure at the rear caliper only suggesting a stoppage between the rear master cylinder and the rear caliper. The only additional components are the lines themselves and the rear modulator. I'm going to the rear modulator next.

Norm has detailed info at My-MC, the ABS II modulator is much more simple than the older version. I suspect the problem is accumulated crud in the Modulator at the lower valve which controls the rear caliper only.

I'll post an update tomorrow soon's I get it checked out. Also waiting to hear from Norm with his suggestions.

Thanks to all for looking.
 
You must log in or register to reply here.
Back
Top Bottom