Secondary Master Cylinder Information

[jfheath]

I'm not sure if those articles give you all the shortcuts.

That's right - I don't often give shortcuts. Generally speaking, I attempt to explain how things work, rather than saying how things could be done. Shortcuts are good to know, if they work for you. Being a big bloke with big hands I need a lot of room to work, and I although I don't make a habit of it, I am well capable of being clumsy. Too many times I have found that taking a short cut ends up taking me much longer, so usually, I don't bother.

But putting in known shortcuts would probably make a good addition to my articles for those that needed to know them. I do need to revisit the Brakes - Avoiding the Pitfalls article. There is a lot of recently acquired information to go in there.

 

[ojm]

Hi again.
I have now rebuild the SMC, against all advise, done 3 rounds of bleeding - and all is working super now, no binding and an ST that stops like never befor !!!!
Thanks for all the help and links.

Ole Mathiasen-Denmark

 

[flip-flop]

well done!

 

[Igofar]

Hi again.
I have now rebuild the SMC, against all advise, done 3 rounds of bleeding - and all is working super now, no binding and an ST that stops like never befor !!!!
Thanks for all the help and links.

Ole Mathiasen-Denmark

When you rebuilt it, did you remove the screen filter cartridge on the backside of the SMC unit and make sure the return port hole was not clogged?
Also, did you make sure the C-clip was put back in correctly (they are directional) so it won't pop back out on you while riding?
Often, rebuilding them, appears to work for a while because the fluid was moved around a lot and may have unplugged the hole for a while, but if you didn't address the backside of the unit, or replace the entire unit, your on borrowed time.

 

[SupraSabre]

When you rebuilt it, did you remove the screen filter cartridge on the backside of the SMC unit and make sure the return port hole was not clogged?
Also, did you make sure the C-clip was put back in correctly (they are directional) so it won't pop back out on you while riding?
Often, rebuilding them, appears to work for a while because the fluid was moved around a lot and may have unplugged the hole for a while, but if you didn't address the backside of the unit, or replace the entire unit, your on borrowed time.

And Larry spoils another celebration!

I did rebuild my 2010's SMC a number of years ago. And it's still going strong today. But like Larry is saying, there are things you need to be aware of when doing it.

 

[jfheath]

I didn't want to chip on on this since you have already taken the plunge and used a rebuild kit - but since you will now have in mind things to think about - did you put any silicone grease on the surfaces that are between the washer and circlip and new piston - including the 'ball' and 'cup' joint ?

This is the inside of the bore of an SMC that had a brand new service kit fitted 2 years prior to the photo being taken. It turns out that it was fitted without any silicone grease. The cup of the 2 year old piston is clearly visible, filled with crud.

 

[ojm]

Hi again.
The SMC on my ST have been replaced at some point, looked like new inside, over and under the c-clip and washer, but the return was clogged badly.
I know about c-clips, I even have the right tools for them, ingoing and outgoing if thats the way to say it, and the sharp edge the right way.
Let`s hope SMC keeps doing what it`s surpose to do !!!


Ole Mathiasen - Denmark

 

[Honda-st-team]

Larry post some picturers of all this work your doing NOT !!! And pictures of these bikes. NOT HAPPENING !!!!

 

[Igofar]

Dang you caught me....its true, I'm just a lonely guy sitting in front of a keyboard, pulling the wool over folks eyes making them think I actually work on motorcycles. I guess I should give away my Handy table lift, and all my tools since I'm not really working on bikes

 

[Honda-st-team]

Post up some pictures of ALL this WORK !!!!

 

[Igofar]

I'm sorry, I don't need to justify myself to you by posting pictures, read some of my reviews
I could post a picture of the quarter ($.25 cents) that you had the nerve to put in my tip jar after working on your bike.
I kept it to remind me of the only person who stiffed me after working on their bike, then insulted me by tossing a quarter in the tip jar

 

[ojm]

Hi All.
As I said in my last post, my new to me 2004 and not 2005 as I was told, stopped like never befor.
And to keep up the good work I ordered some new pads for the rear brake.
Put them in yesterday.
The old pads had a strange wear on them, like heel-toe wear, my thought were that this SMC have a big impact on the rear brake.
Tested the sidemovement on the caliper, befor putting the new pads in, seems ok- big mistake.
Vent for a very very short testdrive,rotor and caliper was so warm I could smell it.
Took the rear caliper out a pulled it apart.
Found this---

 

[jfheath]

Took the rear caliper out a pulled it apart.
Found this---

Oh dear. Yes - that would do it.

That is one of the two slider pins that allow the caliper to to move across - the pistons apply the pressure to the pad on the outside, the action of pressing the pistons out, moves the caliper outwards, pulling the pads onto the inside surface of the brake disc. The other slider pin is on the caliper bracket. The red parts are the slider pin on the bracket - pin and boot. The loose green parts are the pin that is cross threaded on your picture, and the much smaller boot that fits into the caliper bracket. Beware the diagrams that show torque values for that green slider pin - some of the Honda diagrams have this part labelled incorrectly. The correct torque is 27Nm. My manual specifies the torque as being 69Nm on the diagram - it seems that it has been confused with the caliper bracket stopper bolt. Torque it to 69Nm and you will likely strip the threads. Hmmm. I wonder.......



That slider pin in your photo appears to have been put in at an angle and is cross threaded. It is quite probable that the thread has been damaged. You certainly need a new slider pin.
If the threads in the caliper are damaged, I'm not sure what the alternatives are - get a helicoil or equivalent fitted perhaps ? I don't know enough about them to be able to say whether that would be a good solution in this situation. Normally that slider pin has a locking agent applied when it is put into place, and it hardly ever needs to be removed. It certainly doesn't need to be taken out to remove the brake calipers. The caliper and the bracket just pull apart when they are free of the brake disc. You may be able to get your slider pin to screw in correctly, but the thread will certainly have some signs of damage. Would you trust that thread on such a safety critical component ? I know that I wouldn't.

While your are ordering that, I would check out the rubber boots that fit into the holes in which the slider pins slide, and get those if necessary (quite likely I would imagine).

With that slider pin at that angle, the caliper would likely be twisting when the brakes are applied, and would certainly not slide as it should to release the brakes after application. There may be other signs of damage - into which Larry @Igofar has carried out some extensive research - involving the retaining clip on the caliper bracket, the stopper bolt and the bracket itself.

Don't take my answer above as the complete solution to the problem - you need some additional information.

Just goes to show, hot back brakes are not always (or just) the SMC.

My favourite cause for dragging rear brake was due to me thinking it was a good idea to fit some old heatshield pads to the the front brake pads. I'll let you think about that one !

 

[ojm]

Hi John.
Thank you for your comments and advice.
So far I been able to recut the threads from the "inside" of the caliper.
After that I was able to turn the slider pin in again and in the correct angle.
Then I put the caliper in the wise and gave the pin all the force I was able to manages, a lot more than 69Nm and I mean a LOT more, nothing to lose at this moment.
It did not break off !! So for now the slider pin is in it`s place and in the right angle, in correct Nm and non-stick agent.

BUT do I trust it, as You said ??

Ole Mathiasen Denmark.

 

[jfheath]

I was able to manages, a lot more than 69Nm and I mean a LOT more

But - as I said - the correct torque for that bolt is 27Nm NOT 69Nm !!

 

[Morguns1cam]

Hello Larry! Hope all is well your way!
I found your post about the different spring lengths in the SMC very interesting, springs don’t normally “ take a set” unless pushed past there intended lengths or subjected to extreme heat, wondering why they did this? Not doubting you at all of course ( if you say it I believe it) just find it’s curious with that many deviations of length! Has Honda perhaps changed the spring length over time? weird man!
Cam

 

[ojm]

Don´t worry John, I read that. And torque was set to 27Nm.

 

[Igofar]

Hello Larry! Hope all is well your way!
I found your post about the different spring lengths in the SMC very interesting, springs don’t normally “ take a set” unless pushed past there intended lengths or subjected to extreme heat, wondering why they did this? Not doubting you at all of course ( if you say it I believe it) just find it’s curious with that many deviations of length! Has Honda perhaps changed the spring length over time? weird man!
Cam

They probably "take a set" just like the springs in various pistol magazines over the years when kept loaded to full capacity.
They are such short springs (coil count) and are worked so many thousand times during a single ride, I can see why they don't hold up.
The older style 03-07 are thicker & shorter, than the newer style (08-beyond) as they are narrower and have a few coils more than the older version.
The older ones are very stiff to compress, and the newer style are very easy to compress.
Not sure why, or if any of this matters.
Just an observation.
Hope your doing well also.
Igofar

 

[MidLife]

My point was the bikes I worked on, and every single smc spring had taken a set at a different length, weakening spring rates probably contributed to the smc unit failing etc.

As an FYI, some ST fanatics in Europe are seeing extended SMC life after replacing the spring with one they have re-engineered.

 

[jfheath]

An interesting thought, but I'm not sure how you could arrive at that conclusion without parallel experiments. Someone who has had the SMC fail and put in a different spring, has then learned something about the operation and issues with the SMC, and is likely to look after it differently afterwards, so it is not a direct comparison.
'Oh look - I've found out how my SMC works and now it is lasting longer than before I knew anything about it'.

I still believe that the proper regular maintenance when flushing/bleeding the SMC is the way to prolong its life.

I can see that springs may weaken and compress over time (although it goes against schoolboy physics and Hookes Law), but I don't think that in itself would result in SMC 'failure'. When the piston cannot return by itself purely because of the spring, an early symptom (before hot rear pads) would be a spongy brake pedal - the first stroke in a properly bled system would push the piston back. As would excess pressure from fluid trying to escape through the compensation port which would be covered by the non returning piston.

Of course, the same symptom appears when the system is just beginning to fail due blockage (corrosion or crud) at the open end of the bore. A stronger spring will just delay the eventual failure - possibly without giving any early warning signs.

I would guess that if the spring is too tightly coiled, then there may not be enough movement for a full stroke to properly pump the SMC to clear it of old fluid when the brakes are bled. No such danger when in operation - the SMC movement is only 1-2mm.

Just a few thoughts based on a handful of observations and experiments. But the stronger spring may have some merits. Clearly, Honda seem to have experimented over the years.