linked brake removal

Some of the comments here are not quite right. On the ST1100 ABS-TCS from 1996 onwards, it is very common for the secondary master cylinder linkage on the left fork leg to seize, which leads directly to the rear brake binding. It is the clevis pin in the linkage that is most likely to seize.
It it's been seized for a long time, the secondary master cylinder won't have moved & you need to check that's not seized too; fit a repair kit which includes a new piston, seals & circlip.
 
Bloxham said:
Some of the comments here are not quite right. On the ST1100 ABS-TCS from 1996 onwards, it is very common for the secondary master cylinder linkage on the left fork leg to seize, which leads directly to the rear brake binding. It is the clevis pin in the linkage that is most likely to seize.
It it's been seized for a long time, the secondary master cylinder won't have moved & you need to check that's not seized too; fit a repair kit which includes a new piston, seals & circlip.
Click to expand...
Very common? I've not read about that here. Must be guys with that issue are uncommonly silent about it. (I confess to harboring an image of ST's being reliable bikes when maintained routinely.)
 
I've owned one ST1100 ABS and my brother currently has one. It was one of the first jobs that I had to do on my 1100A. Brother had locked brakes and I sorted his out this year in January. New pistons and seals all round, new pads and that linkage was frozen solid. The Pin#11 would not budge, and the washer for the split pin were all seized in place. I brought it home to work on in my garage. I could not move that bow shaped bracket in relation to the pivot casting with the bearings #12 - except by clamaping it in a vice and slowly levering it back and forth.

It is hidden behind that grey shroud and tends to go unnoticed. The needle roller bearings are fine - protected by oil seals. The central pivot point, as @Bloxham said - it is the clevis pin - part #11, the washer on the rear and the split pin part #10 that rust together and lock the entire assembly solid.

It is no coincidence that Bloxam, my brother and me all ride roads in the UK.


ST1100 SMC Exploded Diagram Coloured.jpg

It had been a long time since I worked on an ST1100. I took this diagram and coloured in the parts that fit together - because it is not that easy to work out when it is all in pieces.
The pink bits fit together, the mauve bits go together. The blue and red arrows help to get things aligned too.

The attachment below is a full A4 size drawing.

Incidentally, another cause for the rear wheel lock up turned out to be the rear pedal - the lever shaft had become corroded in the hole in the alloy 'step'. So althought the pedal moved, the spring was inadeqaute to overcome the resistance of the corrosion. So that had to come out, get cleaned up, greased and put back. (I'd gone armed with new spring and circlip. They weren't needed but I replaced them anyway)
 
jfheath said:
I've owned one ST1100 ABS and my brother currently has one. It was one of the first jobs that I had to do on my 1100A. Brother had locked brakes and I sorted his out this year in January. New pistons and seals all round, new pads and that linkage was frozen solid. The Pin#11 would not budge, and the washer for the split pin were all seized in place. I brought it home to work on in my garage. I could not move that bow shaped bracket in relation to the pivot casting with the bearings #12 - except by clamaping it in a vice and slowly levering it back and forth.

It is hidden behind that grey shroud and tends to go unnoticed. The needle roller bearings are fine - protected by oil seals. The central pivot point, as @Bloxham said - it is the clevis pin - part #11, the washer on the rear and the split pin part #10 that rust together and lock the entire assembly solid.

It is no coincidence that Bloxam, my brother and me all ride roads in the UK.


ST1100 SMC Exploded Diagram Coloured.jpg

It had been a long time since I worked on an ST1100. I took this diagram and coloured in the parts that fit together - because it is not that easy to work out when it is all in pieces.
The pink bits fit together, the mauve bits go together. The blue and red arrows help to get things aligned too.

The attachment below is a full A4 size drawing.

Incidentally, another cause for the rear wheel lock up turned out to be the rear pedal - the lever shaft had become corroded in the hole in the alloy 'step'. So althought the pedal moved, the spring was inadeqaute to overcome the resistance of the corrosion. So that had to come out, get cleaned up, greased and put back. (I'd gone armed with new spring and circlip. They weren't needed but I replaced them anyway)
Click to expand...
Correct John, it is likely worstened by the UK weather together with salt on the roads. When the clevis pin seizes, it takes a toll on the solid bronze bush in the linkage too. I've bought a couple of 12mm ID x 14mm OD bushes but not tried fitting them yet. Would likely need to lock the bush into the alloy with some bearing-fit.
 
Well I've rebuilt with repair kits my secondary master cylinder (SMC) and rear brake master cylinder -all linkages are free and all callipers are rebuilt & nothing seized.
Now I've got a problem - pump the rear brake a few times and the rear brake locks up - release the rear-most bleed nipple on rear calliper and this releases some pressure & wheel turns again. At the same time, the secondary master cylinder also has pressure in it and holding the rear brake on. It is not the rear calliper, if I release the rearmost bleed valve, it lets the pressure out & turns freely.
It's almost like I've got a one way valve allowing pressure in the rear brake circuit that's operated by the SMC and not releasing it once the rear brake pedal is released. The rear master cylinder must be ok as I can bleed the rear circuits.
The SMC is in the normal released position.
I'm running out of ideas !
 
Bloxham said:
It's almost like I've got a one way valve allowing pressure in the rear brake circuit that's operated by the SMC and not releasing it once the rear brake pedal is released.
Click to expand...

Good analysys....this is most likely what your SMC has turned into now.

John, our worldwide SMC authority, will most likely chime in and expand on that.
 
From what I've read here, few if any guys have been able to rebuild their SMC successfully and have it work like a new one. The ports are simply too small and never get cleaned out properly.
 
SMSW said:
From what I've read here, few if any guys have been able to rebuild their SMC successfully
Click to expand...

Some have. Depends on your skill level. You have to know what to look for.

Could be a matter of spacing.

@Bloxham is showing some solid abilities and understanding of the system and John might be able to help with his troubleshooting.
 
You can buy used parts but maybe there are few ABS versions sold that go for parts... in my head I thought you could buy both used and new parts for overhaul and repair.
 
SMSW said:
From what I've read here, few if any guys have been able to rebuild their SMC successfully and have it work like a new one. The ports are simply too small and never get cleaned out properly.
Click to expand...
SMSW said:
From what I've read here, few if any guys have been able to rebuild their SMC successfully and have it work like a new one. The ports are simply too small and never get cleaned out properly.
Click to expand...
True and my SMC was quite clogged up with ancient brake fluid. I was able to clean it up and fit the new piston, 2 seals, spring, circlip and rubber boot. The fitting on the side of the SMC (which is the brake fluid inlet) does have some sort of one way valve in it. I'm going to take this off and check it tomorrow.

My rear master cylinder was also quite clogged inside so I fitted a new kit to that too. I don't think the rear brake fluid on this bike can have been changed for many years.

When I bought the bike, the ABS was not working and someone had removed the warning lights. After I fixed the ABS, I thought I was done !
 
Bloxham said:
Some of the comments here are not quite right. On the ST1100 ABS-TCS from 1996 onwards, it is very common for the secondary master cylinder linkage on the left fork leg to seize, which leads directly to the rear brake binding. It is the clevis pin in the linkage that is most likely to seize.
It it's been seized for a long time, the secondary master cylinder won't have moved & you need to check that's not seized too; fit a repair kit which includes a new piston, seals & circlip.
Click to expand...
Got 4 ABSII ST1100s - 1/2 million miles between them - no SMC seized as of yet ... ;)
 
This is the one-way valve from the SMC in my VFR800 but they're all much the same . It is quite easy to pick out the inner blue "Mercedes logo", under that you will find a spring-loaded ball so don't lose that or the spring. There are a couple of hair-thin ports through the body and obviously the mesh that need to be cleaned; I made sure I could jet brake cleaner through the ports and that everything was squeaky clean before reassembly.
IMG_7008.JPG
 
increasing said:
You can buy used parts but maybe there are few ABS versions sold that go for parts... in my head I thought you could buy both used and new parts for overhaul and repair.
Click to expand...
Decades of neglect, incompetent/incomplete fluid flushing/replacement seizing modulator pumps, numberless ham-fisted wheel removals/installations knocking up wheel sensors...
 
TerryS said:
This is the one-way valve from the SMC in my VFR800 but they're all much the same . It is quite easy to pick out the inner blue "Mercedes logo", under that you will find a spring-loaded ball so don't lose that or the spring. There are a couple of hair-thin ports through the body and obviously the mesh that need to be cleaned; I made sure I could jet brake cleaner through the ports and that everything was squeaky clean before reassembly.
IMG_7008.JPG
Click to expand...
Yes that's the one Terry, I removed & cleaned it when I rebuilt the SMC. I'm going to take it out again & check it.
 
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