Secondary Master Cylinder - FAILURE!

[uptoblackwood]

After Dave's observation, i.e. rear outside brakes still recieve +/- 33% of the braking power via the SMC....AND....the fact that disconnection of the connecting rod to the SMC won't really release the stuck piston....I vote for the "stomp on the back brake pedal" to try to free the stuck piston.

 

[uptoblackwood]

No way for me, IGF. I like my linked system!! A lot....

 

[Mellow]

I talked to a guy who claimed he removed all (3) calipers and swapped them out with some off another honda sport bike of some kind. No more linked system, no more SMC. I wonder if this would be an option for us?
IGF

Looking at the diagram in the manual, sure looks like you could cap off the PVC where that hose goes to the rear caliper and cap off that part of the rear caliper and essentially, the SMC would move but not do anything.. .I think.. just not sure I'd try it... You bleed the smc when you do the rear caliper so the fluid is separate.

I like my linked brakes as well.. sure wish they'd done it like other non-smc setups.

 

[MidLife]

Looking at the diagram in the manual, sure looks like you could cap off the PVC where that hose goes to the rear caliper and cap off that part of the rear caliper and essentially, the SMC would move but not do anything.. .I think.. just not sure I'd try it... You bleed the smc when you do the rear caliper so the fluid is separate.

I like my linked brakes as well.. sure wish they'd done it like other non-smc setups.

Yes, completely separated on the hydraulics side. This would work.

 

[Mellow]

So... is there such a thing as a banjo bolt plug? or a banjo bolt without the holes you could use to block off the fluid coming from the SMC/PVC hose at the rear caliper? Would be a little messy but would work I think for at least a roadside repair which disables the linked brakes but allows you to safely get back home for a repair.

Does that make sense?

 

[MidLife]

So... is there such a thing as a banjo bolt plug? or a banjo bolt without the holes you could use to block off the fluid coming from the SMC/PVC hose at the rear caliper? Would be a little messy but would work I think for at least a roadside repair which disables the linked brakes but allows you to safely get back home for a repair.

Does that make sense?

Yes it does.

-- Number one would be to bleed off the pressure that has built up in the line to the rear caliper (initial braking pressure from the SMC plus all the pressure built up from the rear brake overheating). Better let things cool off first.
-- Then plug the line as you suggest

Then we'd have full functionality of the completely independent front circuit to the 4 outer, and the rear activating the middle rear and middle front.

Once we found out what the plug should look like, I'd like to keep one in my repair kit!

In Forest's case, there is a chance that no plug would have been required. If the very high pressure that trashed his rear brake was not able to push back the SMC piston, there is little chance it would have ever gone back at all, acting by itself as the plug we are looking for. Forest could have bled off the pressure to the rear and then the connection can be tighten again with little chances of the two outer on the rear ever activating again.

 

[MidLife]

I have a question about R/R the SMC for any of you who have done it.
If I remember correctly, the service manual states to drain the rear MC before removal.
Will removing the SMC interupt the front MC or lines?
I plan on bleeding the entire system tonight anyhow. I'm just curious.
Thanks
IGOFAR

Have a look at the schematic: http://stwiki.notonthe.net/twiki/bin/view/ST13/LinkedBrakingSystem

The front is completely independent hydraulically. Honda had to design it like that. So if anything happens to the rear system, you still have enough independent front braking power left.

 

[Mellow]

Right... and you wouldn't want to simply empty the rear fluid as then you would only have front brakes.. by putting the bolt in the caliper to block off the fluid from the smc/pvc you still have an enclosed system and front and rear brakes, but not linked... you wouldn't loose braking, just the linked brake function... but I think that's better than being stuck or causing more damage. I'm only suggesting the bolt as a roadside repair if you can't free up the plunger. Heck, I'd even continue on a long trip like that but would be questionable with a sticking smc.

 

[MidLife]

Right... and you wouldn't want to simply empty the rear fluid as then you would only have front brakes.. by putting the bolt in the caliper to block off the fluid from the smc/pvc you still have an enclosed system and front and rear brakes, but not linked... you wouldn't loose braking, just the linked brake function... .

You'd loose your two rear outer, right?

The pedal would just activate the middle on front and rear.

 

[Mellow]

You'd loose your two rear outer, right?

The pedal would just activate the middle on front and rear.

I can't tell looking at the manual, I've always hated the way they did this part of the manual. I'll try to look closer once my eyes are un-crossed.

 

[Kevin_56]

I can't tell looking at the manual, I've always hated the way they did this part of the manual. I'll try to look closer once my eyes are un-crossed.

Per the WIKI link, you will have less rear brake due to disabling the fluid flow from the SMC. But you will have some rear brake.

Kevin

 

[Raj_Zin]

What I fail to grasp here is why this factually well documented dangerous failure is not recall material?

+1 There have been what seems like many instances of the SMC failing just on this forum. And the consequences of failure could be catastrophic. Why has there not been a recall addressing this defective design?

-STeve

 

[uptoblackwood]

Thanks for the observations and post, Igofar...

 

[ChucksKLRST]

Thanks for the observations and post, Igofar...

The rebuild can be done on the bike, Took me about an hour to R/R the innards and clean the bore out. But then, you will need a good bleed job done. Paying attention to turning the SMC up to the proper position during the bleed procedure.

 

[Blrfl]

+1 There have been what seems like many instances of the SMC failing just on this forum.

I added a poll to this thread. It won't be very scientific, but it might give some idea how many "many" is.

--Mark

 

[dduelin]

OMG. More than 40% have had a failure.

 

[uptoblackwood]

Yeah...and after more folks take a good look at their brake system....I'll bet there are a lot of folks who will say they get a lot fewer miles out of their rear brake pads....and....

After looking at my spare SMC that I bought from a 2004 bike with 13,000 miles on the OD at crash...I'd say the corrosion at the top of that piston was unacceptable and likely to be or soon become a problem. This may be a bigger problem than previously thought....even if the failures result in just dragging brake pads. I hope everyone votes in the poll.

 

[dduelin]

I believe 90% percent of the SMC's going bad is due to contamination, and improper bleeding (not tilting the unit, and waiting to long to flush system out) Do it once or twice yearly.
CHeap insurance.

See post #3. I have long believed this.

 

[uptoblackwood]

See post #3. I have long believed this.

That may be the case, Dave, but I am very careful about following procedure when changing fluid...and I always do the scheduled work on time or even ahead of time. Add to that...my bike is garaged unless I'm riding...with the exception of the 10 days I parked it in Santa Fe last month.

 

[dduelin]

That may be the case, Dave, but I am very careful about following procedure when changing fluid...and I always do the scheduled work on time or even ahead of time. Add to that...my bike is garaged unless I'm riding...with the exception of the 10 days I parked it in Santa Fe last month.

Forest, there are the other 10%.