Come on Honda, I expect more from your engineers!

I am underwhelmed with Honda's engineering of the Secondary Master Cylinder unit.

It appears that the SMC piston has once again stopped moving smoothly (or perhaps at all) in the cylinder. This is probably due to moisture entering at the piston rod sealing boot, causing corrosion at the cylinder opening, which I've encountered before.

Hmm... let's examine the history of the SMC for my 2006 motorcycle:

• Purchased in December of 2009 with almost 3,000 miles (2,917 in fact).
• Rebuild SMC in June of 2010 at 8,622 miles.
• Rebuild (2nd time) SMC in August of 2012 at 56,175 miles, and decided to purchase a replacement.
• Installed replacement SMC in August of 2012 at 56,999 miles.
• SMC now frozen in January of 2013 at 66,100 miles.

Now a bit of analysis:

• The original SMC lasted approximately 8,000 miles before failing (I think this may be a generous amount of miles, as the SMC most surely had begun to fail before it was noticed).
• The rebuilt original SMC (actually just a through clean up, lubrication, and reassembly) lasted approximately 47,000 miles before again failing.
• The replacement SMC lasted approximately 9,000 miles before failing.

In conclusion, it appears that an OEM or OEM replacement SMC when fitted to my motorcycle has a rather limited life expectancy of 8,000 to 9,000 miles. However the life expectancy of the rebuilt SMC when fitted to my motorcycle is closer to 50,000 miles. That's quite the difference.

Come on Honda, I expect more from your engineers.

I've got >76,000 miles on my bike and no problems with the SMC (knock on wood). My wife's bike has around 12,000 miles and same thing there too. I do have a SMC rebuild kit in my parts spares just in case.

Is your bike exposed to wet environments often?

Not to keep beating a dead horse... but, isn't this the same "tried and true" technology that's been around since 2003? I had over 20k on my new 2005 without issue.

I have found that even though you can purchase a re-build kit, that the only way to do it correctly is to purchase the entire assembly. Honda will not allow dealerships to "rebuild" and SMC's either, the reason being, that the bore becomes pitted where the disk sits, and even though you put a new smc inside this bore, the pitting from the previous damage allows moisture to slip by contaminating the area, often quicker than before. The only safe way to repair a damaged one is to replace the entire unit, then do a complete brake bleed job, doing the correct procedure. When you rebuilt yours did you follow the service manuals recommendation and put silicone grease on the ball joint and under the boot area for more protection?
While I agree this is really a poor design, they do and can last along time with proper care.
Anytime I wash my bike, or come in after the rain, I dry this area with a motorcycle hair dryer.
Most of the damaged SMC's I've replaced were probably due to poor brake bleeding procedures, by not tilting the SMC during the process, which keeps all the bad stuff right there in that area and it works like cancer.
.02

By the logic of the OP, my impression of the SMC is opposite. The original one on my 2005 purchased 2/2006 with 1820 miles is working fine at 115,538 miles. A trouble-free well engineered design.

The SMC on the 96 'n later 1100 ABSs have caused no problems. Maybe because it's siniSTer. :crackup At any rate, I've never read (that I recall) of one of them failing. Different design than either version of the 1300.

(This coming from a natural leftie. )

I have a post on here with graphic photos of the SMC failure on my bike with around 30K https://www.st-owners.com/forums/showthread.php?113419-Is-This-The-Dreaded-SMC-Failure&highlight= . Honda changed the entire assembly and didn't even blink an eye. When I filed it with the NHTSA, there had only been two other reports that I could find. It will never get fixed at this rate- just be aware and check it often. FWIW, I always unhinge the left brake and bleed it properly; it didn't help.

82k miles on mine, and as of the last ride it was still working. My poor bike also sees very bad weather- lots of rain, some snow, high humidity, and lots of road salt spring and fall.

Now that I post this, it will probably act up!

I don't even want to know what my '05 looks like, since I'm not sure if it was ever "proper bled"! 4:

Not sure what the '04s is like either, since I haven't had time to do anything to its brakes yet. :

Hey SupraSabre, your close enough to ride down to my neck of the woods and let me do a courtesy bleed for ya!

Igofar said:

Hey SupraSabre, your close enough to ride down to my neck of the woods and let me do a courtesy bleed for ya!

Click to expand...

Larry, someday, I just might take you up on your offer, but I'm afraid they will require acomplete system rebuild and not just a bleed! 4:

Bring it on! order the parts and call me on the white courtesy phone
Ride safe
Larry

"Knock on wood" 72,526 miles no problems.

Following up on my earlier post about Honda engineers, perhaps I was a wee bit hasty in my judgement that the SMC had failed a second time. Apparently the symptoms I observed; dragging rear brakes, and an immobile SMC, were not due to the SMC freezing up.

With an eye to minimizing down time for the motorcycle, I spend the first part of the morning rebuilding the original SMC with the factory rebuild kit. With the rebuilt SMC in hand I began the task of swapping out the current (presumingly frozen) SMC, imagine my surprise when I found that the current SMC piston was moving as freely as the one I had just rebuilt. Okay, the rebuilt SMC now sits on the shelf in readiness, and the current SMC is back in service.

On to the rear caliper where the brake pads looked terrible; worn down to the time-to-replace-me groove in the pad material, with cooked brake residue stuck to the brake pad plate. All this in just over 6,000 miles, no wonder my fuel mileage was deteriorating!

Cleaning up the caliper and caliper sliding pins did not reveal any problems, indeed the only oddity found was that the two little tabs on the brake pad spring pad (#5 in the parts fiche) were both bent over enough to prevent an easy install of the wheel side brake pad. Straightening up the tabs allowed the brake pad to slide into place easily, now with both rear brake pads installed the rear brake caliper is ready to be bled.

Bleeding was completed without the aid of any vacuum pumps, just a litre of brake fluid, a motion-pro check valve, and a short wooden stick.

The brakes are once again operating as I think they should; no pumping of either lever or pedal to 'build pressure', no lengthy pedal travel to apply braking effort, and no differential pedal movement as a function of releasing the lever.

Anna'sDad said:

The brakes are once again operating as I think they should; no pumping of either lever or pedal to 'build pressure', no lengthy pedal travel to apply braking effort, and no differential pedal movement as a function of releasing the lever.

Click to expand...

Well that was short lived! Less then 2 weeks have passed (~800 miles) since I wrote that, and the rear brakes again are dragging.

Whilst no pumping is required, the travel for the brake pedal has increased. Additionally, pedal actuation can be felt through the hand lever, more often when releasing the lever after having engaged both brake pedal and lever, as when coming to a complete stop. One other observation; the pedal also feels as if it continues to move (slightly) after the initial resistance is met, this is most noticeable when using just the pedal.

On a side note, I've noticed a markedly reduced braking effect (requiring significantly greater pedal and lever forces to slow the motorcycle down) the day after having ridden on wet & salted roadways. Unlike an automobile where the brake effectiveness returns after a few moments of brake use, the ST1300 brake effectiveness requires a day or two of riding.

These events are typical of my experiences with the ST1300 brake system, which again leads me to say ?Come on Honda, I expect more from your engineers?.

The pedal drop felt after releasing the hand lever sounds like textbook air in the SMC or elsewhere in the rear pedal circuits fed by the rear master cylinder.

dduelin said:

The pedal drop felt after releasing the hand lever sounds like textbook air in the SMC or elsewhere in the rear pedal circuits fed by the rear master cylinder.

Click to expand...

I imagine you are correct in your assumption, I expect to find air when I bleed the rear brake circuit again.

The oddity for me is that after a successful(?) brake bleeding experience, the brakes behave exactly as one would expect, no excessive pedal travel, no softness, and excellent braking performance. However within a short period of time/miles, the brakes begin to behave poorly, additional pedal travel required, softness, and reduced braking performance.

My understanding of a hydraulic brake system is that when the air has been purged from the system, it stays purged until some event allows air to enter the system. The usual events that introduce air into the system are, component replacement, and forgetting to refill the master cylinder reservoir during the bleeding process.

This phenomenon of the reappearing air in my brake system has me puzzled. I think in the near future I may just pull all of the components off the motorcycle and clean/rebuild each of them. A bit of a shotgun approach, but at least I'll know that each component has been inspected, and is functioning.

Might I have a try at bleeding the brakes? Your not to far from where I live. Let me know?

Yes, I agree about searching for a compromised part in the system. For a long time I haven't had a need to bleed the system any less than the recommended 12,000 miles and don't really notice the degradation of the system prior to the service although the pedal and lever are firmer after doing so. However, I performed the service once early in my ownership and did not get all the air out of the SMC circuit and had pedal drop make a re-appearance in a short time. I rebled it at 3 or 4,000 miles and ran a lot of fluid through the proportioning valve and SMC before a big bubble came out. It is critical to remove and hang the SMC tilted up at least 15 degrees.

acedantinne said:

Might I have a try at bleeding the brakes? Your not to far from where I live. Let me know?

Click to expand...

Very Generous.

PM sent.