The inner workings of the secondary master cylinder ( SMC)

cycleguy1800 · Mar 22, 2015

Just thought I would show the inner pieces of the seondary master cylinder , the check valve and screens are an interesting pieces to view , clean brake fluid is must , a great amount of vacuum is barely enough to pull brake fluid thru the check valve and both of the screens. This SMC was a sticker , piston assembly was hanging up.

Cheers

v8-7 · Mar 22, 2015

Did you find out why it was sticking ?

cycleguy1800 · Mar 22, 2015

There was a brown crud outside and inside the bore of the SMC due to a slow build up of road grime under the boot , the tiny fluid compensation port was blocked by the sticky inner piston and seal , this won't allow for any fluid expansion when the brake fluid heats up, the only place for the fluid to go is inside the outer calper pistons and the rear brake starts to self apply , it's like keeping the brake pedal depressed ever so lightly.

BakerBoy · Mar 22, 2015

Where are you at cycleguy? Wondering as climate has some effect, as does the bike model year (2008 and later it is slightly redesigned).

cycleguy1800 · Mar 25, 2015

BakerBoy said:
Where are you at cycleguy? Wondering as climate has some effect, as does the bike model year (2008 and later it is slightly redesigned).

We have alot of cinder dust on the roads here in the spring, some of that and water got past the SMC boot and into the bore. A far as the 2008 SMC, Honda uses a different front brake pad for 2008 and newer ST1300's and the PN# is different , perhaps the pad is larger or thicker which would cause a PN# change on the 2008 and newer bikes as that would affect the SMC assembly as well, the SMC bore rebuild kit has a different PN# as well. It would be intersting to see if the bore diameter is the same from a 2006 verses a 2008.

Al Gully · Mar 25, 2015

Are you just going to clean up the used SMC parts or are you going to purchase a kit.
Some have purchased the entire SMC.
Others have said that the used piston was oval and that was causing the piston to stick in the bore also.

BakerBoy · Mar 26, 2015

cycleguy1800 said:
We have alot of cinder dust on the roads here in the spring, some of that and water got past the SMC boot and into the bore. A far as the 2008 SMC, Honda uses a different front brake pad for 2008 and newer ST1300's and the PN# is different , perhaps the pad is larger or thicker which would cause a PN# change on the 2008 and newer bikes as that would affect the SMC assembly as well, the SMC bore rebuild kit has a different PN# as well. It would be intersting to see if the bore diameter is the same from a 2006 verses a 2008.

Front calipers, pads, SMC ... all were redesigned for 2008 and later models. While we don't know the reason why, it does seem reasonable that Honda engineers at least took that same opportunity to redesign the SMC piston and to improve water drain around the boot. https://www.st-owners.com/forums/showthread.php?127809-SMC-Upgrade. However, it is merely speculation as to why the calipers and pads were changed.

cycleguy1800 · Mar 28, 2015

Al Gully said:
Are you just going to clean up the used SMC parts or are you going to purchase a kit.
Some have purchased the entire SMC.
Others have said that the used piston was oval and that was causing the piston to stick in the bore also.

I replaced the entire SMC assembly as I wanted a new check valve and screens which are not availbile at all , they were also gummed up , you can't even get the o-ring which seals that assembly.

Now has anyone bolted on a BRACKET SUB-ASSY. for 2012 Honda ST1300A 06454-MCS-R02 on an early ST1300 model , say like an 2003 ?

The inner workings of the secondary master cylinder ( SMC)

cycleguy1800

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v8-7

cycleguy1800

BakerBoy

It's all small stuff.

cycleguy1800

Al Gully

BakerBoy

It's all small stuff.

cycleguy1800