Hi, I own a 2005 Honda ST1300. I should mention that the bike had been sitting idle for a long time. A brake issue has come up: the center piston in the rear caliper isn't extending—I thought it was completely seized. I removed and cleaned all the calipers and added fresh fluid, then began the bleeding procedure step-by-step: front upper left (OK), front upper right (OK), PVC (OK), rear center (no fluid), front right center (OK), front left center (OK), rear outer (OK). Everything I’ve found points to the SMC; can anyone confirm this, or suggest another way to check it?
ST 1300 Brake problem
- Thread starter Elgodrico
- Start date
There are several articles (or were) about the brakes on the forum, including one recently.
Standard test is to lie on the floor, bike on centerstand, roll the rear tire with your foot and push the SMC with your hand.
This should stop the rear wheel.
Releasing the SMC should allow the wheel to be spun with your foot again.
I'll see if I can find some articles.
EDIT: here's a good start... search Articles > ST1300 in the menu for "ST1300 - Brake Maintenance - Avoiding the Pitfalls"
Standard test is to lie on the floor, bike on centerstand, roll the rear tire with your foot and push the SMC with your hand.
This should stop the rear wheel.
Releasing the SMC should allow the wheel to be spun with your foot again.
I'll see if I can find some articles.
EDIT: here's a good start... search Articles > ST1300 in the menu for "ST1300 - Brake Maintenance - Avoiding the Pitfalls"
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You can manually exercise the SMC by hand to check if it is moving the 3 mm or so it needs to create pressure in the rear caliper or if it is frozen in place. The SMC should take very little pressure to compress. If it moves freely then with the motorcycle on the center stand have an assistant rotate the rear wheel while the SMC is manually compressed. The rear brake should stop the wheel. You can do this alone by lying on the ground on the left side of the motorcycle and moving the rear wheel with one foot while you compress the SMC by hand.
When bleeding the brakes it's a good idea to first suck out the old fluid from the master cylinder reservoirs with a turkey baster or syringe. Refill w/ new juice and then bleed the system. I pump a couple of full reservoirs through each bleed nipple, flushing out the old fluid.
What did your old brake fluid look like? Was it tea colored or worse? We have had guys report the stuff looked like beef stew (or worse). This is bad news for the SMC because it's ports are so tiny and easily clogged. Rebuilding attempts almost always lead to a repeat failure.
What did your old brake fluid look like? Was it tea colored or worse? We have had guys report the stuff looked like beef stew (or worse). This is bad news for the SMC because it's ports are so tiny and easily clogged. Rebuilding attempts almost always lead to a repeat failure.
- Joined
- Nov 10, 2007
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- 96
- Age
- 63
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- Vancouver, British Columbia, Canada
- Bike
- 1&2&3-2005 ST1300ABS
Here is a link showing a great video by @STRider showing how the SMC works. As you can see, it doesn't travel a lot.
So when your moving the SMC by hand turning the rear wheel with your left foot, a little movement will stop the rear tire. The SMC actuates the 2 outer pistons in the rear caliper.
The brake pedal actuates the inner piston in the rear caliper.
My SMC locked up for the first time on my #2 ST1300 when I rolled it out of storage for the first time this year for a ride in January. A bike sitting or put away with moisture under the SMC boot will cause this.
Glad I had a rebuilt SMC in stock. Still woking great to this day.
The way I check the SMC when on level ground at a stop light, I release the brakes and roll the bike forward and reverse and see if there is any resistance from the braking system.
https://www.st-owners.com/forums/th...ster-cylinder-rebuild-smc.133460/post-2612152
So when your moving the SMC by hand turning the rear wheel with your left foot, a little movement will stop the rear tire. The SMC actuates the 2 outer pistons in the rear caliper.
The brake pedal actuates the inner piston in the rear caliper.
My SMC locked up for the first time on my #2 ST1300 when I rolled it out of storage for the first time this year for a ride in January. A bike sitting or put away with moisture under the SMC boot will cause this.
Glad I had a rebuilt SMC in stock. Still woking great to this day.
The way I check the SMC when on level ground at a stop light, I release the brakes and roll the bike forward and reverse and see if there is any resistance from the braking system.
https://www.st-owners.com/forums/th...ster-cylinder-rebuild-smc.133460/post-2612152
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I disagree with @Elgodrico about everything pointing to the SMC - nothing that you have said in post#1 points directly at the SMC. There may be an issue to be looked at later, but the rear centre piston not moving has got nothing to do with with the SMC: The rear centre piston on the ST1300 is operated only by the rear pedal / master cylinder from the line that runs direct from the rear master cylinder to the rear caliper centre piston.
There's no point looking at the SMC for trouble until you can get that rear centre piston to move. The rear pedal operates two lines and one of those lines goes through the proportional control valve and a lot of hoses - so the amount of pressure that you can get on the rear centre piston by pressing the rear pedal is rather limited. Try a mechanical device (I have never used one), or compressed air applied to the hole for the forward / central banjo bolt of the rear caliper.
You may need to undo / replace those three massive bolts that hold the two caliper halves together. I don't think that the pistons can be removed without the halves being separated - but the centre piston is shorter - so I may be mistaken about that.
You also said - Rear Centre - No Fluid. Which is odd. Check your rear master cylinder. It is tucked behind the alloy 'step' that contains the footpegs, bolted to it from the inside. (pictures in a later post). The banjo bolt should be a long one because it has two hoses from two banjo unions attached to it. One for a hose that goes forward toward the front brakes (it operates the two front centre pistons directly), and another which goes backwards to the rear centre piston.
I'm wondering if there is no fluid because someone has removed that line to the rear caliper centre piston and has fitted a normal / single banjo bolt.
There's no point looking at the SMC for trouble until you can get that rear centre piston to move. The rear pedal operates two lines and one of those lines goes through the proportional control valve and a lot of hoses - so the amount of pressure that you can get on the rear centre piston by pressing the rear pedal is rather limited. Try a mechanical device (I have never used one), or compressed air applied to the hole for the forward / central banjo bolt of the rear caliper.
You may need to undo / replace those three massive bolts that hold the two caliper halves together. I don't think that the pistons can be removed without the halves being separated - but the centre piston is shorter - so I may be mistaken about that.
You also said - Rear Centre - No Fluid. Which is odd. Check your rear master cylinder. It is tucked behind the alloy 'step' that contains the footpegs, bolted to it from the inside. (pictures in a later post). The banjo bolt should be a long one because it has two hoses from two banjo unions attached to it. One for a hose that goes forward toward the front brakes (it operates the two front centre pistons directly), and another which goes backwards to the rear centre piston.
I'm wondering if there is no fluid because someone has removed that line to the rear caliper centre piston and has fitted a normal / single banjo bolt.
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You sure? Proof?
I think you got it backwards. The SMC actuates the 2 outer pistons in the rear and the rear brake actuates the center piston of the rear (and fronts actually) caliper.
The ST1300 linked brake system is quite complex to my simple mind. There is a lot happening when you apply the front, apply the rear, and it does differ if the bike is rolling or stopped.
Great visual toy and flow chart with lots of checks to play with (not mine) And fluid routes are very important. Note the fluid systems join at some of the Banjo fittings thus run to both front and rear brakes when check valves allow.
https://mjc-506.github.io/st1300braketoy/
That is linked from here:
https://www.st-owners.com/forums/threads/st1300-brake-system-simulator.183390/
Another great brakes read, page 2 and 3 add a lot of info and insight to the operations. One needs to understand IGOFAR s check valve pics to really understand the SMC operation.
https://www.st-owners.com/forums/threads/st1300-secondary-master-cylinder-rebuild-smc.133460/
More on flow systems:
https://stwiki.notonthe.net/bin/view/ST13/LinkedBrakingSystem
Great visual toy and flow chart with lots of checks to play with (not mine) And fluid routes are very important. Note the fluid systems join at some of the Banjo fittings thus run to both front and rear brakes when check valves allow.
https://mjc-506.github.io/st1300braketoy/
That is linked from here:
https://www.st-owners.com/forums/threads/st1300-brake-system-simulator.183390/
Another great brakes read, page 2 and 3 add a lot of info and insight to the operations. One needs to understand IGOFAR s check valve pics to really understand the SMC operation.
https://www.st-owners.com/forums/threads/st1300-secondary-master-cylinder-rebuild-smc.133460/
More on flow systems:
https://stwiki.notonthe.net/bin/view/ST13/LinkedBrakingSystem
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The diagrams that I produced in this article about bleeding brakes shows how the various components are connected. Download the pdf in post #1.
https://www.st-owners.com/forums/th...g-all-the-air-out-of-the-brake-system.156754/
Some people may have got confused if they have owned a VFR - they have an extremely similar system - but the rear pistons are plumbed the opposite way round compared with the ST1300.
Some photos:
Rear Master Cylinder Fitted to the inside of the step. Note the double length banjo bolt
And here - the normal view from the right hand side (ignore the rust). The top hose goes forward to the front right hand side of the steering head.
The lower one goes to the rear caliper centre piston - via the metal tubes above the battery and across the swinging arm.
https://www.st-owners.com/forums/th...g-all-the-air-out-of-the-brake-system.156754/
Some people may have got confused if they have owned a VFR - they have an extremely similar system - but the rear pistons are plumbed the opposite way round compared with the ST1300.
Some photos:
Rear Master Cylinder Fitted to the inside of the step. Note the double length banjo bolt
And here - the normal view from the right hand side (ignore the rust). The top hose goes forward to the front right hand side of the steering head.
The lower one goes to the rear caliper centre piston - via the metal tubes above the battery and across the swinging arm.
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When rebuilding a caliper, one can often remove the pistons by applying a compressed air hose to the brake line port and pressurizing the caliper. If the pistons are not corroded in place, they will shoot across the workshop and any residual brake fluid will spray onto any painted surfaces nearby. If you try this method, position the caliper so that it aims into a stout cardboard box to catch the piston and fluid. Cover the caliper with an old towel to further reduce brake fluid spray and loss of the piston.
I had a Guzzi's caliper that was frozen and the compressed air method to eject the pistons failed because of extensive corrosion that required a new caliper.
So more of work Werę done. I’ve opened the smc, and give it a nice clean, rubbers were okay, and there wasen’t so much dirt on it, the little hole cleaned as well. Still center piston not going out, when we put presured air through the bleeder, piston is out so canal in caliper Works fine. In my opinion there is blockade on the line somewhere between smc and rear caliper. Two outer pistons are operated by foot pedal and that is working fine, as the front brakes.
- Joined
- Nov 10, 2007
- Messages
- 96
- Age
- 63
- Location
- Vancouver, British Columbia, Canada
- Bike
- 1&2&3-2005 ST1300ABS
Rube Goldberg could have done better. When it's working correctly it does work really well but is utterly intolerant of deferred or neglected maintenance.
Please - Read my previous post (#6 on my screen). The SMC does not have any line that goes to the rear centre piston. I agree there may be a blockage but if it is still the centre piston of the rear caliper, then hunting the lines from the SMC to the rear caliper will not find it.
Well - that would let air into the system. First open the forward / centre bleed valve on the rear caliper with a tube attached while gently pressing on the rear brake pedal. If no fluid comes out, then you already have air in the system .
If fluid does come and it is consistent with being pumped by the brake pedal, then secure the bleed valve and apply the brakes again.
But I guess that you have already done that.
Some suggestions.
I repeat - these are some random suggestions to consider when deciding how to proceed. It’s not a sequence. Fluid isn’t coming out of the centre piston bleed valve. These are suggestions only to find out why and what could possibly fix it. It’s a lot of messy work.
I’ve made some suggestions because I do not know the bike’s history. Some people have been known to do some really stupid things with the ST1300 brakes ‘to make them better’. In fact the ST1300 brakes are superb. They just need to be serviced properly and at the designated intervals. I’ve ridden 155,000 miles on ST1300s and my brakes have never had these issues - and you can see from the rust, that I ride in all weathers and on gritty, salty Uk roads. The above photos were taken while I was addressing those issues.
If fluid does come and it is consistent with being pumped by the brake pedal, then secure the bleed valve and apply the brakes again.
But I guess that you have already done that.
Some suggestions.
- Check that the SMC is actually operating the two outer pistons. If the wheel is out, you can see the pistons move. If not, you can use a feeler guage between the back of the pad and the piston to see if it gets trapped.
- Assuming that the brakes are not connected like the VFR and we have the SMC operating the two rear outer pistons and the rear centre piston is only operated by the brake pedal - then check that the bleed hole is not blocked. Carefully remove the bleed valve - see if the brake pedal manages to get fluid out then. If there is a blockage, it will shoot out like a cork. You don't want to be on the receiving end of that.
- While the valve is out, check on the flow of fluid to the open bleed valve. Clean the threads and carefully put it back with fingers. Turn the screw anticlockwise until you feel the screw drop off the end of the thread, and then gently screw it in clockwise with fingers. Finish off with a spanner.
- This is the only way I can think of that someone before you might have managed to reverse the centre / outer piston operation. Check that the brake lines on the swing arm are as shown - ie the outside one is connected to the centre piston. The inside one (8) is connected to the rear outer pistons - rear most bleed valve. I'm wondering if a previous owner has coupled them up like the VFR.
- Slacken the forward / centre piston banjo bolt. Pump the brake pedal. Does the bolt weep fluid ? If so the line isn't blocked.
- If that doesn't reveal anything then it really is time to look at the double banjo bolt. It’s going to be messy. Have rags and poly sandwich bags handy. You might want to drain some of the system of fluid so that it doesn't go everywhere.
We know that the Master Cylinder is pumping fluid. But not to the rear centre. Check that the top hose is the one that runs towards the front of the bike.
You could get another single banjo bolt (say from the rear caliper outer port) and attach the line for the rear centre piston to the master cylinder using the single banjo bolt. Undo the rear centre piston Banjo bolt. When you pump the brake lever, fluid should flow easily. Or you should have enough clout to shift anything blocked in the pipes. If fluid doesn’t flow then the line is blocked somewhere. - Then reconnect the banjo to the caliper centre piston inlet port. Tighten it up enough to not allow leaks and try pumping fluid through and into the bleed tube from the caliper. With nothing else connected there should be plenty of pressure to dislodge something.
Thought - is it an ABS model ? If so do the ABS pumps whirr when you turn on the ignition ? - It is possible that the piston is stuck absolutely fast inside the bore. Corroded solid. If so, even if you can get it out, the bore isn't going to be useless. Might be time to get a new one.
I repeat - these are some random suggestions to consider when deciding how to proceed. It’s not a sequence. Fluid isn’t coming out of the centre piston bleed valve. These are suggestions only to find out why and what could possibly fix it. It’s a lot of messy work.
I’ve made some suggestions because I do not know the bike’s history. Some people have been known to do some really stupid things with the ST1300 brakes ‘to make them better’. In fact the ST1300 brakes are superb. They just need to be serviced properly and at the designated intervals. I’ve ridden 155,000 miles on ST1300s and my brakes have never had these issues - and you can see from the rust, that I ride in all weathers and on gritty, salty Uk roads. The above photos were taken while I was addressing those issues.
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Going up from rear caliper i found something strange, near battery... There is rear ABS pump missing...2 of the hoses connected toghether, and two of them blind end...
That would explain the absence of fluid to the rear centre. There are four lines to the ABS pumps. In and out for both the outer pistons and for the centre piston.
It seems that the in and out for the outer pistons have been joined together, but not the lines for the centre piston.
So I had the right idea - someone has disconnected the line to the centre piston. I never considered that they would have removed the ABS pump. Chances are that they have done the same at the front.
I guess that it easy to do. The non Abs models have the same plumbing as the abs models - except the non abs models have a short pipe to bridge the place where the abs pump would fit. You can probably buy that part - short metal brake pipe. Are you sure that your model originally had ABS? The white label under the seat on the frame tube will show St1300-4 or St1300A-4. I don’t think that there was a 2005 model in Europe, but it might say ST1300-5 OR ST1300A-5. The A models had Abs and electrically adjustable screens.
That being the case, I would guess that the centre piston and bore have been dry for so long that they are corroded beyond recovery. But I cannot know that for certain.
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