ST1300: Rebuilding the SMC, Rear MC and Rear Caliper

SupraSabre

48 Years of SoCal Lane Splitting/Commuting-Retired
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Joined
Nov 20, 2005
Messages
9,500
Location
Cedar City, Utah
Bike
12/04 ST 1300s
2024 Miles
000145
STOC #
5901
A few weeks ago, Byron came over to swap out some tires for me. I also replaced the brakes. Once we got the bike back together, I took it for a spin and the rear brakes did not feel right.

I pulled back in to the garage and back up on the HF Lift and we proceeded to bleed the brakes. Dropped the bike back on the centerstand and it would not budge, the rear tire was frozen. Back on the centerstand and start bleeding them again. Still a frozen tire! We tried a few more times and still couldn’t get it to move. We even did a complete brake bleed and still no luck.

Frustrated, I decided that I would need to rebuild the rear brake system and since I didn't have the parts, I decided to just finish up my project bike by taking parts from the other ’04 and I have been riding that since.

I ordered the rebuild kits for the SMC, the Rear Master Cylinder and the Rear Caliper and some new rear brake pads. When the parts came in on Friday, I thought I should get in touch with Byron and see if he wanted to help me with them. He didn’t even hesitate! :D

Sunday morning we met for breakfast and then had to stop by Pep Boys to pick up some brake fluid. And we were ready to tackle the brakes…well maybe.

We decided it would be best to start with the front and rebuild the SMC (since both of us have heard of others having a similar problem of their brakes when their SMC went south). We removed the hoses and even though removing them were a bit of a PIA with all the fluid and that, but we got them off and then pulled the whole unit off the bike.

Boy, you sure have to have the right spring clip tool to get those C clips out! Other than fighting the dust cap, and once we were able to get the C clip off, it wasn't too bad working on the SMC since we took the complete brake caliper off the bike. We finally got it apart and started putting the new parts in. Although, when we were disassembling the SMC, we came across a filter (small cylindrical) thingy with an o-ring that we didn't see any pictures of nor reference to in the manual (that we could see). we cleaned it up and put it back in place.

We were then able to install the caliper and mount back on the bike, along with hooking back up the hoses and such.

Byron wanted to try it out before working on the rear caliper or the rear mc, so we filled the reservoirs and started bleeding. When we started bleeding the SMC, we heard a bang and whoosh… Not a good sound. Apparently we didn't get the SMC back together where the C clip was all the way in and it popped apart with brake fluid going all over! We cleaned it back up and put it all back in and this time made sure the C clip was going to hold!

We went back to bleeding, but after several attempts, nope, the rear tire was still stuck!

After a quick break (not brake) Byron (being totally frustrated that that didn't fix the problem) was ready for the rear caliper (although I wanted to start on the Rear MC) But I went along with him and we started on the rear caliper. Pulling it apart wasn't too bad, then cleaning it of course, but trying to get those seals in were a real PIA. Byron was able to get them to go in, but I sure wasn't having much luck with them.

We got them reassembled with new pistons when Byron decided to read the manual again and noticed that we should have put some grease on the outer seal, instead of brake fluid! Dang! We popped the pistons back out (compressed air is wonderful!) cleaned up the top seals and greased them with a little brake grease. Back together again. Then put the two halves of the caliper back together and I had bought a new rear caliper mount, so I greased the slides and got the caliper temporarily back in place.

I figured Byron was going to say let’s bleed it and see if that fixes it, but I still wanted to rebuild the Rear MC first. I was able to convince Byron. So we started on taking the side foot step apart. I’m sure they could have designed this better, but we were able to get everything apart and get to the master cylinder.

It was much easier than the SMC because the shaft end piece came off, so you didn’t have to fight with that dust seal when trying to get to the C clip. Once apart, we were able to clean it and started reassembly. The secondary seal on the main part of the piston was sure a PIA to get on. And then the rest of the assembly went well.

While we had the step off, I replaced the brake pedal (the original had a good scrape under the pedal, that was starting to rust). Besides, I wanted this bike looking good, not a crash rebuild that it is! ;) When pulling the pedal off, I noticed that the C clip was missing. So after putting on the better looking pedal from ebay, I found a paper clip and Byron help me with making a “safety wire” type fix on it.

We replaced the MC and Byron started reading the book again and saw that the pedal was to have a certain distance from the MC. So we measured that out and proceeded on reassembling the step to the bike. That wasn't too bad, but we found that you can’t put the little cover on back until the step is in place. Hooking up the brakelines was a real PIA since it’s one of the last things you do, but trying to get all three crush washer in there…oh joy! But we did it!

So, now all we had to do was to install the rear tire and bleed the system. We went back through the complete brake bleed procedure and by the time we had gotten to the rear most valve of the rear brake, we had brakes and they were not freezing up the rear tire!

I was just about to put the mufflers back on and decide to start it up first. Byron said something about making my wife mad and I just sort of laughed that off when I hit the starter. Of course about that time my wife comes out to the garage! LOL Have you ever heard what these bikes sound like without their mufflers? WOW! Where can I get some straight pipes? Those Harleys would not stand a chance in a noise contest! :D

I put the mufflers back on and took the bike for a little spin. So nice to use the rear brake and not have the rear lock up! :run1:

After that Byron headed on home, I cleaned up the garages enough to get my wife’s car back in and I was done for the day. I think I’m going to go through (since I still have the plastic off) the bleeding sequence one more time, just to make sure that all the air is out of the system. Then I’ll put the bike back together.

What a day. We started on the bike around 11am and finished around 7PM or so.

So we rebuilt the SMC, Rear MC and the Rear Caliper and then bled the system. I have rebuilt a motorcycle front Master Cylinder and auto drum brakes (including the slave cylinders) in the past, but this was a first for me to rebuild a disk caliper, much less the SMC & the rear MC.

Neither Byron nor I were convinced after pulling the Rear MC and the Rear Caliper apart that they would solve the problem of the brakes locking up the rear tire, but I figured what the heck at least I would know that those were not the problem areas if that didn't fix it. And needless to say we were elated when the rear tire was still spinning after we finished!

Thanks for the help Byron! You’re a great friend!

I wished I would have taken some pictures (I took a couple but I should have taken more) but trying to get my phone out when you have brake fluid all over your hands makes it a bit hard! :eek:4:
 
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SupraSabre

SupraSabre

48 Years of SoCal Lane Splitting/Commuting-Retired
Site Supporter
Joined
Nov 20, 2005
Messages
9,500
Location
Cedar City, Utah
Bike
12/04 ST 1300s
2024 Miles
000145
STOC #
5901
Don't forget to replace that brake lever circlip !!!

....
Thanks for your comments and yes, the circlip is on my list of things to order. But it has gone over 34,000 miles without it and it will stay in place due to the Rear Master Cylinder.
 
Joined
Nov 10, 2007
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1,608
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61
Location
Vancouver, British Columbia, Canada
Bike
1&2 2005 ST1300ABS's
STOC #
8562
jfheath said:
I never noticed the requirement for 'brake grease' - is this the silicon based grease that they use for hydraulic seals - we call it rubber grease ?
And I call rubber grease in Canada O-Ring grease
Dow Corning MOLYKOTE? 55 O-RING GREASE
In the safety Data sheet, they call it Silicone Grease

55 O-ring lubricant is a light beige to pink colour and is a lithium soap, thickened, silicone grease. Temperature ranges from -85 to 350 degrees F (-65 to 177 degrees C). Not recommended for lubricating silicone rubber O-rings and seals, 150 g tube.


http://www.dowcorning.com/applications/search/products/Details.aspx?prod=01889826
 

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