Dragging back brake

[Bdelloid]

Hi all,
I have an 02 ST1300 pan non abs, and I have a dragging back brake, I have stripped and split the rear calliper fitted new seals and pads, cleaned both front callipers and fitted new pads, replaced the delay valve, checked the SMC and re greased the roller bearing and that seems ok and is working, checked the back brake MC and again that seems ok as well, the dragging has reduced from before, but still when I apply the rear brake it draggs on release but reduces after a while but not totaly free,
I have never had any trouble sorting brakes out before but this is driving me nuts,
Any ideas please as I am running out of them

 

[Kevcules]

Usually it's the SMC. Lay down on the left side of your bike, spin the rear tire with your foot and use the SMC to stop the wheel. Then the wheel should release and spin quickly again. Lots of play in the SMC travel indicates a worn SMC or there's still air in the system.
Then there's the rear caliper bracket that gets deformed. Check the caliper bracket guide hole for "fluting" and check your brake pad guides to see if they're still straight.
Lots of information in the articles section above. Good luck...

 

[ST-Traveler]

SMC- Secondary Master Cylinder on you left front caliper. It becomes corroded and failures are quite common. The ST1300 has a linked brake system so when you apply the front brake the SMC on the left front caliper will also activate the rear brake ( linking the front and rear together) .
I would start with the testing mentioned by Kevcules first.

 

[Buckeyechris]

Usually it's the SMC. Lay down on the left side of your bike, spin the rear tire with your foot and use the SMC to stop the wheel. Then the wheel should release and spin quickly again. Lots of play in the SMC travel indicates a worn SMC or there's still air in the system.
Then there's the rear caliper bracket that gets deformed. Check the caliper bracket guide hole for "fluting" and check your brake pad guides to see if they're still straight.
Lots of information in the articles section above. Good luck...

@Bdelloid

I had the same problem with my '05 a couple of years ago. There's a lot of articles and posts on this forum that addresses some of the typical contributors to the problem you're experiencing. The following is a link to an an article that I wrote about my experience that may help you diagnose your situation: https://www.st-owners.com/forums/threads/st1300-smc-replacement-caliper-rebuild-lessons.184310/

Before I replaced the Secondary Master Cylinder, I tried replacing the piston. While that worked for a while, it did not permanently solve the problem. Eventually, the new piston stopped moving in the bore and stuck in place 99% of the time. Rebuilding the SMC is rarely effective, because it is nearly impossible to seat the new boot correctly. Consequently, the incorrect seal allows water and other debris to enter the plunger/piston area that leads to corrosion and sediment buildup.

It seems that the complicated plumbing of the linked braking system tends to make a routine flush and refill of brake fluid anything but ordinary. Although it is a bit of pain, flushing the system annually, instead of every 2 years (or more as some tend to do), tends to keep the circuit between the SMC and rear caliper functioning properly.

As you will see from my article, I replaced both the SMC and Rear Caliper Bracket to resolve my problem. Hopefully, your equipment is better sorted. If not, replacing those parts is fairly straightforward. Best of luck in your quest!

 

[jfheath]

If you have had your rear caliper off, then you might want to check out this document - download the pdf in post#1.

This deals with most of the easily fixable problems created by having the brakes / wheel off. Usually the little things that are not commonly known about.

Article [13] - ST1300 - Brake Maintenance - Avoiding the Pitfalls | ST1300 Articles

A close hands-on look at the Honda ST1300 braking system. These are personal observations about the things that can go wrong, why they go wrong and what can be done to keep things working sweetly. Updated April 2020 and to address more recent observations, to include information about the SMC...

www.st-owners.com

Then there are issues at the front wheel. eg Not many people new to the ST1300 know that you MUST follow a particular sequence when installing the front wheel. If you don't then that can cause the SMC to operate, which causes the rear wheel to drag.

Article [13] - ST1300 - Maintenance - Front & Rear Wheel Install and Front Axle Animation | ST1300 Articles

Animated sequence to show the correct procedure when installing the front wheel into the forks of a Honda ST1300. The right hand side of the bike is the side with the brake lever. Left is the clutch lever side. This is the convention used in the Honda manuals. The video and the photo below...

www.st-owners.com

And of course - check that the SMC is working properly - when you apply it by hand - as if you were applying a brake lever - the back wheel should stop turning and when you release the SMC it should free up instantly. Given the age of the bike, it has to be suspect - but there are so many 'fingers' issues where things have not been assembled correctly. Having too much air / movement in the SMC isn't going to cause the rear wheel to drag. But the SMC not releasing the rear brake will.


I had such a problem years ago - which turned out to be me applying too much rubber grease to the slider pins and boot. Smoking hot rear brake on the point of locking up solid.

Find what is causing it before you fix it.

You've had both calipers off. Take note of the chrome retainer clip into which the tab end of the brakes fit in the caliper bracket. The front and rear retainer clips are different, the rear one having a ridge, the front ones not having a ridge. If you have fitted the rear clip to the front left caliper bracket, then the front pads will not release after the brakes have been applied - this will casue the front left brake to drag, which will casue the rear brake to drag even more.

You've clearly worked on a lot of other bikes. The ST1300 is not like a lot of other bikes and often requires a different approach. Assume that you don't know how to fir a wheel; how to replace calipers and find what you need to know on the forums.

I have a lot of articles about wheels, brakes and SMC. Here's a link to just mine - but read others as well.

 

[Igofar]

Why rebuilding,or replacing the SMC piston won’t work.
The return port gets clogged, and is easily damaged trying to remove this cartridge to attempt to clear it.
Best to replace as an entire assembly.
Also, when neglected, or having too much air In the system, the top plate of the SMC can have too much movement, tilt, and cause this type of damage, which can then catch and lock stuff up without warning.
This type of damage will not be visible from the outside and is often missed.