View Poll Results: Has your ST1300 had a SMC failure?

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  • Yes

    41 40.20%
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    61 59.80%
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Thread: Secondary Master Cylinder - FAILURE!

  1. #1
    uptoblackwood's Avatar
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    Secondary Master Cylinder - FAILURE!

    I've read many posts about the ST1300 SMC failures on this site and have noted the cautions about the resulting rear wheel lock up or dragging brake pads. It happened to me...last weekend. Just over 60,000 miles on the OD of my 2007 ST1300. I keep the bike garaged...but I don't hesitate to ride in the rain. Texas, rain? Yeah right.... What did happen and where the culprit water came from....I was in NM for 10 days performing at a music festival...this last month. It's monsoon season in NM and it rained a bit everyday. My bike was sitting in the condo parking lot all week. I had no time to ride during the festival.

    Pre '08, the SMC had two small holes (not at the bottom of the cylinder) that were supposed to drain water from the rubber boot covered piston. Those holes didn't work. Post '08, Honda revised the SMC housing with a cut in the cylinder and a drain trough. Seems if water sits in the area around the rubber boot....the boot doesn't seal good enough to keep it out of the piston area and corrosion around the piston keep it from retuning to it's original position after use. Symptoms might start with simple dragging on the rear brake disk....act then...'cause if you don't, it will lock up and you've got big trouble.

    In my case, I was close to home. I was coming to a stop light and applied equal pressure on both front and back brakes and I felt a slight pull in the rear. After I stopped I looked down and around....and all seemed well. I started up at the green light and I knew the rear brake was dragging on the disk. I *only* had two miles to get home....so I headed to the barn. I pulled in the driveway, got off the bike, looked carefully at the back brake/rotor....and it was bad news. The disk was damaged beyond repair and the almost new brake pads were melted together from pad section to pad section. The pistons didn't apply pressure evenly and the violence associated with the SMC failure BENT the heavy brass backing plate on the outside brake pad. I'll post up photos later this afternoon after I upload them to my Smug Mug account.

    The GOOD NEWS. Al Lamb's Honda (Dallas Honda) has a great service department. The two lead guys in the department both ride ST1100s and know the drill. Ted Poovey, the service manager, has been with Al Lamb's Honda for 33 years!! I have had the best of luck using this dealership....though both of my ST1300s....so only good things to say about these folks.

    Parts have been ordered and are on the way. Warrantee all the way!! No fights, no issues, just good service.

    Forest

    PS DON'T mess around with this SMC issue. If you feel those back brakes dragging...get the bike in for a checkup. A totally locked back wheel will take you down fast. Photos later....

    Puritanism - The haunting fear that someone, somewhere may be happy. ----H.L. Mencken
    2005 ST1300 RIP at 59,000 +-
    2007 ST1300 ABS
    http://forestaten.smugmug.com/Motorcycles

  2. #2
    st1300r's Avatar
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    Re: Secondary Master Cylinder - FAILURE!

    Could have been a lot worse. Glad it was just some mechanical damage.
    Carl, SToc#7163, ST1300 '04

  3. #3
    Be Thou My Vision dduelin's Avatar
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    Re: Secondary Master Cylinder - FAILURE!

    Glad it was just inconvenience and not worse.

    This is a good reminder that the recommended flush of the linked brake system is important at the interval Honda gives. The LBS design is not especially forgiving of stretching or ignoring this item.


    Dave

    Honda ST1300
    Honda NC700XD
    Honda CH80

  4. #4
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    uptoblackwood's Avatar
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    Re: Secondary Master Cylinder - FAILURE!

    I agree, Carl. Another note for those of you who might suffer this problem in the future. The rear caliper has three pistons. The outer two pistons are in the direct circuit driven by the SMC. If the rear brakes are dragging and you suspect the SMC...don't use your front brakes as you limp to a safe stopping place. The SMC is on the front left caliper and is activated in the linked system through a relationship with the front left brake caliper. Use your back brake foot pedal. It activates the inside piston on the rear brake caliper. You'll have to be careful 'cause you won't have much braking power.....but it beats the risk of hitting those front brakes again and having a complete lock up.

    To get my bike to the shop, I removed the rear wheel and replaced the rear brake pads. I then put everything back together again and removed the bolt holding the SMC piston rod. This way, I could apply both front and back brake without activation of the SMC or back outside pistons. I wouldn't recommend any long distance runs this way....but it got me to the dealership about 5 miles away from my house...just fine.

    Forest

  5. #5
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    Re: Secondary Master Cylinder - FAILURE!

    Dave...I am very good about changing fluids and always do them at or before scheduled in the manual. I had just flushed both clutch and brakes about 5,000 miles before this happened. This SMC issue is really about the rubber boot covering the piston. It doesn't do the job of keeping water out of the top piston area. The resulting build up of corrosion causes the piston to stick. You can't see the mess unless you remove the rubber boot...and that's not a thing required or even mentioned in the service manual. Honda knows that there was a problem and changed the design in '08. I hope it works correctly....now.

  6. #6
    Be Thou My Vision dduelin's Avatar
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    Re: Secondary Master Cylinder - FAILURE!

    Use of the rear brake pedal alone still generates force to the SMC - the rear pedal includes a circuit that drives the center piston in both front calipers so use of the rear pedal alone can still activate 33% of front brake force.

  7. #7
    st1300r's Avatar
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    Re: Secondary Master Cylinder - FAILURE!

    Is there an easy way to remove/reinstall the rubber boot to clean with out messing it up?

  8. #8
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    Re: Secondary Master Cylinder - FAILURE!

    Dave...yep, with delay and at only 33%....better than the entire force being used. I didn't mean to encourage riding past even the brake "dragging" event. In my case it wasn't a dramatic event....just a slight scraping sound and the drag was very, very slight. The ST has a lot of power and torque...and can push though easily until the damage is quickly done. That's why I disconnected the connecting arm to the SMC for the ride to the dealer.

  9. #9
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    Re: Secondary Master Cylinder - FAILURE!

    Carl, I haven't tried but I have a spare set of brakes/calipers that I purchased off of ebay for "cheap". They are in like new shape. I'll break down the SMC and see. I know the piston seal is retained by a clip....so the boot may be easy to remove. I read on site on one of the threads...that someone had pulled the boot and filled it with food grade silicone (dive shop).

  10. #10
    Be Thou My Vision dduelin's Avatar
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    Re: Secondary Master Cylinder - FAILURE!

    I would still debate that corrosion that prevents the piston from returning to the relaxed position begins in the bore itself - below the seal on the SMC piston - not above it. Any corrosion above it wouldn't affect the piston movement in it's bore because it moves down and away from that area. Corrosion above the piston seal with the piston in the normal relaxed position, that is outside of the cylinder bore, couldn't affect the SMC sticking at any point in its normal range of movement.

    If the SMC is not leaking brake fluid it is impossible for water to leak down from above it. When the brake is applied there are many inch-pounds of pressure exerted on the piston, probably hundreds of times the pressure of water sitting above the seal under no pressure at all.

    I do not doubt you had trouble and it is right in the SMC but there is probably corrosion in the SMC bore itself that caused the problem, not above it, and the corrosion in the bore started it all.

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