Secondary Master Cylinder - FAILURE!

[uptoblackwood]

I'd love to see a Honda recall on this....and get to take a look at the resulting data. Too bad this isn't an easier overhaul project (well...seem it is...except it take time, time and more time to complete). If it were, it would be great to do some these SMCs and some of the techSTOCs around the country. That way we'd get to see what things look like at different mileage and riding habits.

 

[Uncle Lumpy]

I've been thinking about this "problem" since shortly after I bought my non-ABS '06. I grew up riding bikes with non-linked brakes. This ST1300 is the first bike I've ever owned with linked brakes. Actually, my previous bikes all had "linked brakes" in that I was the link! As the rider, I was the "modulator" between the front and rear brakes, judging under each situation how to "modulate' the brakes. I'm not sure that I want Mother Honda deciding this function for me.

I've thought about removing the SMC from the equation altogether. I think the way I'd do this is to eliminate the hydraulic line from the SMC to the proportional control valve (PCV), remove the proportional control valve (PCV) and remove the hydraulic line from the PCV to the rear brake. Additionally, since this would mean the rear brake disk would only be using the middle piston, I think I'd look for a way to rework the rear brake hose setup so that the rear brake pedal activates the outer two pistons on the rear brake instead.

From the schematic in the link provided in post #52 above, it looks as if the "SMC" circuit is hydraulically separate, but this can't be. From the bleeding procedure, it is part of the rear brake master cylinder system hydraulically. So, I'd have to find a way to isolate the section I listed above as wanting to remove from the rear brake master cylinder hydraulic system. I'm thinking a bolt or two in the right places will work, but I'd have to look more closely at the system.

I really hate the idea of the poorly-designed SMC system ruining a trip (or worse, causing me to have an accident due to rear brake lockup). At 33K miles I've had no issues yet, but the system appears to be a time bomb waiting to go off.

Thoughts?

Uncle Lumpy

 

[dduelin]

I took the left side caliper and SMC bracket off tonight to look under the boot. I was pleased to find the pushrod and other visible components clean & dry, shiny, and w/o corrosion. I did not remove the circlip and look under it - there might be corrosion under the top seal in the upper bore but likely the boot would have to have been leaking water for this to happen. In my case the boot was still pliable and giving a tight seal at 96,648 miles. I applied a smidge of silicone grease to the sealing edge of the boot and put it back together.

When removing the LH caliper for brake fluid servicing the service manual warns to remove the upper joint bolt (pushrod end) first, then the lower pivot bolt. If this sequence is not done it would easy to place undue strain on the pushrod and possibly dislodge the boot or damage the pushrod. A bent rod would pull the boot to one side and also possibly cause it to leak water, not to mention cause sticking or jamming. Just something to pay attention to when removing the LH caliper to bleed the brakes. Something else to check is that the needle bearing around the lower pivot bolt is not seized up and possibly preventing that little spring from retracting the SMC piston.

 

[uptoblackwood]

Another thread with kit parts numbers....and a lot more of the same kind of infomation we've all come all too familar with, i.e. stuck SMC. https://www.st-owners.com/forums/showthread.php?86791-SMC-Rebuild-Kit

 

[tempus]

I just found out that the SMC is the problem I had with my rear brake dragging. At one point the bike was in my garage and the rear tire would not move at all. I let it sit overnite and I could at least load it on to a trailer to take to the Honda dealer. The said the part is on back order. They expect to receive the part in approx 2 weeks. I have a 2007 with approx 9000 miles and still under warranty. The dealer said that Honda would not pay for a rebuild, it had to be a new one. Part#06454-MCS-G02 listed as a bracket sub assembly. Just thought I would add another story to the growing list regarding this part.

 

[jduff8505]

I also belive the spring gets weak, although I can't prove that.

I could if you have an old and new one to compare.

Jeff

 

[jduff8505]

I had this exact same failure at ~7.5K miles. The previous owner apparently did not treasure the bike as I do, since it was less than a year old when I bought it and it looked like it sat outside under a tree. I now baby it and it hasn't spent the night outside since. Amazing how quick they can deteriorate if you don't at least keep them under a cover.

 

[tempus]

I had this exact same failure at ~7.5K miles. The previous owner apparently did not treasure the bike as I do, since it was less than a year old when I bought it and it looked like it sat outside under a tree. I now baby it and it hasn't spent the night outside since. Amazing how quick they can deteriorate if you don't at least keep them under a cover.

I also purchased my ST from a previous owner who had it for less than one year. He also lives in OK just west of Fort Smith, Arkansas. But the bike was always housed. He had 3 other bikes and took very good care of all of them.

 

[jduff8505]

Keeping them out of the weather is about the best thing you can do for them. Even if you just have a carport or a bike cover you will extend the life by several years.

 

[tempus]

Maybe a good question for a second poll is "If you have had a SMC failure, what year is your ST?".

 

[coreyasl]

I have an '03 with 72k miles. I've had N issue with dragging rear brake for a long time. The first time I noticed it (@10k) I was getting on the freeway, and could tell right away something wasn't right. I started to pull over while doing what I always used to do on my dirt bikes etc, - tapping the rear brake pedal. After a few flicks, it released itself, and I continued on my merry way. This happened a few more times before I could get it into the shop. They told me it was a bent guide pin (or something) it was a while ago. But then it kept happening. Since I knew how to deal with it, I just lived with it until now. It's currently in the shop for tune up etc, and I told them to replace the SMC. It's on backorder but when it's finished, I'll let you know if it changes anything. =

 

[dduelin]

People bend guide pins by not getting the forward tabs on the brake pads up in the notch they fit in the caliper. The pads will almost.........not........fit....... then the pins are forced into place. The sticking SMC is unrelated to bent guide pins. Of course if a dealer is telling you something I would take it with a grain of salt.

 

[tempus]

Another question that would be interesting to see the replies to is: Is there anyone who has replaced the original defective SMC, also had to replace the 2nd replacement SMC?

 

[bikerblackie]

Add me to the list. My rear brake won't release until a few minutes have passed. Releases instantly by releasing pressure anywhere between SMC and rear caliper. (bleeder valves outside rear, or hose on output of SMC). Releasing pressure on center front calipers or center rear has no effect, of course there is no pressure to release at these points. Parts on order.

 

[Simmons1]

Hmmm....

http://www.motorcycledaily.com/2011/12/honda-brake-recall-affects-11-gold-wing-gl1800-model-years-2001-2010-and-2012/

I wonder how similar the SMC's are?

My SMC failed on my 05 when it was around 8 months old and had 12K miles on it. The bike has 91K on it now and I have had no other problems with it. Bike gets ridden in the rain a lot and rarely gets washed.

 

[v8-7]

Add my '07 with 15K miles ( always garage kept ) to the sticking SMC list.

The bike had ~ 8k miles on it when I got it last year and I bleed the brakes at that time using the procedures on this site.

The rebuild kit is on order from Honda and hope it will be here in time for the trip next Thursday to the Blue Ridge gathering.

So a few questions :

Does the rebuild kit come with a new spring and a new boot ?

It looks like the old boot needs to be cut off, or is there a way to get the old boot off without cutting it ?

Where did you guys drain the brake fluid from ?

Chuck, I see you did yours on the bike . Would you do it that way again ?

Looks like wrestling the snap ring off may be a bear , but once I get the boot out of the way, maybe it will access easier ?

Any other advice ?
when

 

[dduelin]

The rebuild kit comes with a new sping and a new boot. The clevis joint comes apart, the rod is threaded into a nut that is integral to the clevis end so you can slip the new boot over the pushrod.

 

[nvrider]

07, 5600 mi rear wheel locked up. in Honda shop. expected Harleys I have had for the last 25 years to have problems. got tired of worring about it so I bought a Honda......Huh.

 

[GregoryA]

I've read many posts about the ST1300 SMC failures on this site and it was my turn. It happened to me a month ago with 12.000 km (st1300a,2008,ABS).The previous owner kept the bike garaged, after <great> washes, for a long period and I supposed that was the reason!!!!!!...
In my island, Honda has a great service Department called HONDA KARANTONIS. We ordered the apropriate part .
The mechanic needed a special tool to remove the old piston because of the corrosion!!!!!
He assembled the new one, packed the piston rod boot with silicone grease, replaced the brake fluid and bled the whole braking system. The cost was 56 euros for SMC, 20 euros for brake fluid and 60 euros for the work.
Everything is ok now, I'd like to thank you all, for your precious help (info,reviews,photos)!!!!!!!!

 

[bwoodsom]

I have an 05 with no ABS. So my SMC seems to be seized. My rear brakes are dragging and I cannot move the SMC. I am trying to order one online here but the descriptions are vague. I have found conflicting part numbers on the forum here as well.
In the image below if I want to order #2 in the graphic below which #2 to I choose. G01 or G02?

Any help is appreciated.
Bob