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
Sadlsor
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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.
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- 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.time . The SMC acuates the center piston in the rear caliper.
The brake pedal acuates the 2 outer pistons 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.time . The SMC acuates the center piston in the rear caliper.
The brake pedal acuates the 2 outer pistons 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
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 tha mount 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 thing the pistons can be removed without the halves being separated - but the centre piston is a smaller length - 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. The banjo bolt should be a long one because it has two banjo unions. attached to it. One for a lead that goes forward toward the front brakes (it oeprates 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 tha mount 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 thing the pistons can be removed without the halves being separated - but the centre piston is a smaller length - 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. The banjo bolt should be a long one because it has two banjo unions. attached to it. One for a lead that goes forward toward the front brakes (it oeprates 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 lenght 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 lenght 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.