2007 St1300 SMC problem

JimGregory said:

Yes spoke to Larry last night. Great guy!
Reg does the weep hole enter into the area UNDER the boot? I have yet to disassemble and examine. Hard to believe that would be the case. The hole actually lets water in?
Maybe it's meant to let brake fluid out in case of a leaky piston seal?

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It's supposed to be a water drainage point. I'm thinking if it lets water out it can let it in. Not sure I'm going to plug it yet. I'm going to check under the boot before I do and see if I can see the drain hole there. If I can't find it under the boot, I won't plug it. My intention will be to keep moisture from getting to the SMC.

dduelin said:

I know that is simple minded but it seems to work and prevents much grief later.

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Not simple minded, wise. I'm just thinking out of the box, maybe a bad idea. I will grease it as the manual says, but I may not plug the weep hole, or I may; I'll know by this afternoon. The shop didn't service mine correctly and caused my issues. Additionally, I paid for the non-service! I don't know what an LBS is.

Look at the SMC and see were the drain hole is. It is outside of the area protected by the boot. There is absolutely no way for water to leak past the boot through the drain hole. It simply allows water above the boot to drain out. If the boot is in good shape, correctly installed, and the drain hole is kept open then water cannot leak past it into the SMC. The manual and common sense indicates a smear of silicone grease on the lip of the boot - the open end - the bell shaped end - will help seal the boot/bore interface.

Theoretically, if water got past the boot it could eventually corrode the bore surface and push rod above the piston seal. Extreme case the piston could seize from corrosion above the piston.

If the fluid is not replaced often enough to forestall loss of essential operating qualities the SMC bore below the seal can corrode from moisture retained in the fluid and the SMC corrodes below the seal.

Hydraulic systems operate by compressing fluid. If there is sufficient seal integrity to retain hydraulic fluid under normal operating PSI (hundreds if not 1000+ PSI under hard braking) and there are no leaks in the brake system....it's theoretically impossible for water under atmospheric pressure to leak past that upper seal into the SMC bore.

Again, simple preventative maintenance should head these issues off or at least see them coming.

Edit: LBS is Linked Brake System. Honda alternatively describes them as CBS combined brake system.

When I came onto this forum 9 years ago there was a very helpful tutorial on a hydraulic system flush in the tech article forum. I printed a copy before the tutorial went off-line.It's about 30 pages in PDF files with text and pictures. I use it every time I flush and replace the fluid. It is involved, as it should be - brakes are a critical maintenance item - but it is easy to follow and it has been very helpful to me over the years. I'm happy to forward a copy to anyone that desire one. PM me an email address if you want it.

LBS=linked braking system.
I would agree with Dave on this one, as long as the system is done correctly, and often, it should fine. A lot of it is just normal care and feeding. Wash the bike or ride in the rain...make sure you dry the SMC area before parking her for the night etc.
Make sure the pivot bearings are always greased with good quality waterproof grease so the unit can pivot freely and smoothly.
The service manual indicates to place grease in boot area, however, this may mean to assist pushing the rim into place, not packing it with grease to collect dirt and trap moisture etc. I also wonder if packing grease behind boot will heat up and melt and cause more issues than not?
I ride my bike 365 days a year, rain or shine, but I also use my motorcycle hair dryer to make sure the important areas are dry every night.
Your results may differ.

Good discussion. Had many times over it seems and my apologies for that. BUT How does one remove and replace the assembly containing the boot? Simply pull the actuating rod and it pulls the boot off with it? Any special technique to re installing? Or should I say seating the boot properly? Is the snap ring BELOW all this?
This may all become apparent to me once I get the bits in hand and a bright light on it. My failing eyes have not shown me much so far.

The service manual is good at detailing the sequence of parts. If you can wait until later tonight I can take a picture of drawings/pics to send to you. The boot sits above the circlip and the boot lip fits into a groove machined into the upper end of the SMC bore. Once in a while I pull the boot up in inspect underneath - I can't remember anything special about doing so except the boot does not like being pulled up. Mine is 154,xxx miles old and still pliable which is kind of amazing.

dduelin said:

The service manual is good at detailing the sequence of parts. If you can wait until later tonight I can take a picture of drawings/pics to send to you. The boot sits above the circlip and the boot lip fits into a groove machined into the upper end of the SMC bore. Once in a while I pull the boot up in inspect underneath - I can't remember anything special about doing so except the boot does not like being pulled up. Mine is 154,xxx miles old and still pliable which is kind of amazing.

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Yes I just looked this thread over and it shown clearly the sequence so no need DD. I wish my boot just pulled up like a gentleman instead of tearing. Maybe I needed to squirt some loose juice in there first.
https://www.st-owners.com/forums/showthread.php?133460-ST1300-Secondary-Master-Cylinder-Rebuild-SMC

Jim have you figured out how to remove the boot without tearing it? Do you unscrew the bolt bracket before removing the boot. I tried to pull my boot up but it did not want to come. I just want to see what it looks like under there.

woodybelle said:

Jim have you figured out how to remove the boot without tearing it? Do you unscrew the bolt bracket before removing the boot. I tried to pull my boot up but it did not want to come. I just want to see what it looks like under there.

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No I have only figured out how to tear it. I have new parts on order and I will be happy to let you know my findings when I get into it. Or likely someone will chime in.

JimGregory said:

No I have only figured out how to tear it. I have new parts on order and I will be happy to let you know my findings when I get into it. Or likely someone will chime in.

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That was my experience as well and that's why I ordered 2 boots so I would have a spare for the next time I service it.

Igofar said:

I ride my bike 365 days a year, rain or shine, but I also use my motorcycle hair dryer to make sure the important areas are dry every night.
Your results may differ.

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Larry, where is the hair on your ST? (Sorry, I just couldn't help myself***)

dduelin said:

Look at the SMC and see were the drain hole is. It is outside of the area protected by the boot. There is absolutely no way for water to leak past the boot through the drain hole. It simply allows water above the boot to drain out. If the boot is in good shape, correctly installed, and the drain hole is kept open then water cannot leak past it into the SMC. The manual and common sense indicates a smear of silicone grease on the lip of the boot - the open end - the bell shaped end - will help seal the boot/bore interface.

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Yep, I just put it together and saw where the drain was above the lip of the boot. Like I said earlier I'll look first. It remains unclogged and the top of the piston area under the boot is greased and under the boot where it connects to the rod as the manual states. For the past two years this is what I've done, clean it out and re-grease, although it kind'a looks like the boot is packed. The system is ready to bleed now.

To remove the boot, I take a pair of needle nose pliers and squeeze the boot in to the rod on two sides and with the with forefinger and thumb pull a non-squeezed side out slowly. Comes right out. The old boot was eight years.

Installed the new boot this morning. Not a big deal but there is no definitive way of knowing that the big end is seated all the way down. I used a socket that just fit in the bore, and a c clamp. Didn't see a need for a lot of pressure on the clamp. The drain was clear, and showing above the boot. Had to remove the mount but the adjustment bolt showed no inclination of moving so it was quite simple.
All was clean inside the boot. I left some residual silicone grease in it but removed the bulk of it. I had packed it full after tearing the boot. Thanks for the advise all.
Jim