Article [13] ST1300 - Secondary Master Cylinder Rebuild- SMC

[Tim D.]

I want to support this posting, as I just worked on my SMC on a 2007 and as you will see from the photos many if not all things that could go wrong did.

Take apart you SMC every 2 or 3 years and service it, I have to replace mine and you do not want to pay for that.

I used this posting to help me take apart the SMC and everything worked as outlined, except I am waiting on parts.

Do not let this happen to you!

 

[roadriderg]

Just finished rebuilding my smc with the latest rebuild kit, 45620-mcs-g04. My bike has 45,000 miles on it. At times I could feel the rear brake sticking and knocking of the front caliper.

When I opened the smc if found that other that a little mushrooming of the piston it was not corroded, everything looked very good. So I cleaned everything out , replaced the piston, a little silicone grease and done. Other than the tricky part of getting the snap ring out it was not too difficult.

At the same time I removed all pads front and rear, cleaned all pistons, calipers and springs and applied a little silicone grease around the base of the pistons. Grease on sliding pins on the calipers. Then I bleed the system according to the manual.
Result seems good, rear rotor is not so hot as before. Front smc does not have the free space as before, seems a little tighter. I checked this with one on a new 2012 on the showroom floor and the clearance on the smc seems the same.
Next this weekend a long ride to verify all is good.

I really wanted a complete unit but was told they are on backorder. That would have been a whole lot easier. But thanks to this forum I was given both info and courage to do the job myself and rebuild it.

 

[4jranch]

Hope it comes out, if not you can always buy the whole MC. You would have to wait for it to arrive though...

 

[randalicious]

Mine's not as ugly as Tim's, but the piston won't budge. Reminds me of Love Shack -- "Tin roof, . . . rusted." Salt water corrosion? Maybe common on all the bikes in our shipment?

Used compressed air at the bleed port, but couldn't get a good seal on the other outlets. So, N/G.

I'm about to try drilling the piston and tapping it for a 10-32 screw, and pulling it out with that. Opened the rebuild kit already, so no refund. If the bore's too munged up, I'm in for paying for a complete assembly anyway.

Bike's down until something good happens.

 

[randalicious]

Finally, something good happened. My plan to drill and tap a bore into the plunger didn't work after the plunger started to spin because of the pressure of the drill and then the tap. It retreated further down in the SMC bore. So, I used an Easy Out to lock into my drill hole and spin the plunger CCW, while gently pulling up. After several hours of tenderly turning it while putting upward pressure on the EO, it finally started to respond and rise in the SMC bore. After it came out far enough, the spring spit it out of the SMC. Good news, the bore is clean! So, after I dry off from being sweat-soaked, I'll continue with the SMC overhaul, then, the brake system bleeding.

HTH somebody that is having the same problem as I did, and want to pay the diff of a new caliper/SMC with sweat equity. May your garage be air-conditioned.

I couldn't have done it without you, Jeff. :bow1:

I can hardly wait for the next Central TX RTE! Maybe I should say this last thing after I test the brakes.

 

[paneuro]

Hi. thank you for the useful article! Accessing the left front wheel SMC and servicing the cyclinder with new piston will solve the rear brake issues? I experience my rear brake use to wear off much faster then the rest and there was an occasion it got like locked up( without any feel to the rear brakes). I have since got it rectified and did send to a service shop to bleed the fluid. However I feel , it may not be enough. I would seriously consider servicing the SMC if its highly recommended to ensure the rest of the brakes are working properly.

 

[randalicious]

I would seriously consider servicing the SMC if its highly recommended to ensure the rest of the brakes are working properly.

If the front left brake caliper/SMC does not move smoothly when you press it forward to push the SMC piston further into its bore, the SMC will need to be rebuilt or replaced.
If the SMC does not move at all, the SMC piston is not free to move, and your rear brake is in danger of locking up.

 

[Simmons1]

Mine just failed for the second time. The first time it failed at around 12K miles when my bike was 6 months old . It took the two different Honda Shops about 10 visits to figure out what was causing the rear brake to drag. 100K miles later it is doing it again. I guess it is time to rebuild or replace it again.

 

[Simmons1]

That bites! Let us know how the repair goes.

Other than bleeding the system being I pain in the butt, I have no complaints. The bike is 10 years old with 113K miles on it, I figure anything can break at time as the miles add up.

 

[FireAndIce]

Just took mine apart as it was not functioning. Mine was full of a white gooey substance! I was told that could be from moisture. The ports were plugged up with the goo. Also took apart caliper, same story. Wacky stuff. New plunger on order. Anybody seen this goo in their system before?

 

[uptoblackwood]

Sorry I missed this thread, Jeff. I'm with you on taking preventative action to avoid the known problem with the secondary master cyl. At 66,000 miles on my '07, mine failed. The result was a locked up rear brake. The rotor was destroyed, brake caliper damaged, master cyl. a disaster. I had no warning. What happens to create this problem is nicely presented in your photos. Water leaks around the top boot and corrosion starts doing it's dirty work. This isn't obvious when just looking at the secondary master cyl. in it's normal use. Honda changed the design of the secondary master cyl.....in I believe '09 (maybe '08). They added a small channel to allow water to drain off of the top boot.

Thanks for this post. Hope all is well with you guys!

Forest

 

[MI-St1300]

The white goop may be a sign somebody used Dot5 fluid in the system. How long have you owned the bike? You can ask Igofar, as I am not a expert, but I think that is what happens when Dot5 brake fluid is put into a Dot4 system by accident. It gets gummed up as the two fluids are not complatable. Maybe somebody will jump in and confirm this or enlighten us.

 

[ST-Traveler]

Now that I have installed a new SMC, I was wondering how to service the unit other that bleeding the brakes?

What is everyone doing to service the SMC?

Is it to take apart and clean?

How often?

There is nothing in the service manual about when or how to service the SMC.

 

[dduelin]

Now that I have installed a new SMC, I was wondering how to service the unit other that bleeding the brakes?

What is everyone doing to service the SMC?

Is it to take apart and clean?

How often?

There is nothing in the service manual about when or how to service the SMC.

Flush and replace hydraulic fluid every 12,000 miles or two years. No short cuts - remove and tilt the LF caliper assembly as detailed in SM and elsewhere. Repeat as needed. That's all the SMC needs besides keeping the drain hole or channel clear.

 

[Gus1300]

Do you recall how many copper crush washers there were on all of the front hoses going to that left caliper? Did you replace those or just reuse them. (One of my pet peeves is the price they charge for a simple copper washer).

If you're not aware, copper crush washers can be annealed by heating to cherry hot with a torch and quenching. Unlike hardening other metals, this softens the copper from its used/hardened state.

 

[uptoblackwood]

DOT 5 brake fluid is not backward compatible with DOT 4, it's silicone based. Even if flushed...the problem with using DOT 5 comes when used with ABS. It foams and really doesn't work in ABS systems.....

 

[STmark1300]

Flush and replace hydraulic fluid every 12,000 miles or two years. No short cuts - remove and tilt the LF caliper assembly as detailed in SM and elsewhere. Repeat as needed. That's all the SMC needs besides keeping the drain hole or channel clear.

The annealing process does not require quenching, but is done to removing scaling. I would not quench it.

 

[Catmandu2]

Great article. I can appreciate it all the more,, as I have gone through the whole smc fail and replacement process. In getting ready to rebuild my original smc,,, I noticed that the revzilla fiche for my 2004 list 4 versions of the replacement piston ass'y,, with only the 3 most recent being still available. I am guessing I would be best ordering the G04 (seem item's #20) ?? CAt'

Honda Motorcycle 2004 OEM Parts Diagram for Left Front Brake Caliper | Partzilla.com

Buy OEM Parts for Honda Motorcycle 2004 Left Front Brake Caliper Diagram

www.partzilla.com

 

[oude geit]

No help on parts....I did away with the SMC after a failure left me sliding to the side of the road. Plugged that tube and re-drilled the caliper for full function.

 

[Igofar]

Great article. I can appreciate it all the more,, as I have gone through the whole smc fail and replacement process. In getting ready to rebuild my original smc,,, I noticed that the revzilla fiche for my 2004 list 4 versions of the replacement piston ass'y,, with only the 3 most recent being still available. I am guessing I would be best ordering the G04 (seem item's #20) ?? CAt'

Honda Motorcycle 2004 OEM Parts Diagram for Left Front Brake Caliper | Partzilla.com

Buy OEM Parts for Honda Motorcycle 2004 Left Front Brake Caliper Diagram

www.partzilla.com

Perhaps I can save you some $$$ and some frustration with your SMC project.
And before all those members who've used the rebuild kit and claimed success, jump in and flame me, let me share a couple pictures with you and a short explanation of why its a waste of money.
The return port in the SMC body is VERY small, and behind it rests a very small filter cartridge, with yet another VERY small orifice.
I'll try and post a couple pictures (from other members) of just how small it is, and why your better off just replacing the entire unit.
While I'm no expert, I have replaced several hundreds of these units over the past few years, and its always the same....
Owner opened up the front of the unit, thought the bore was clean, and put it back together etc.
Only then to find out that no, or very little, fluid was passing through the screen(s) and port(s) to reach the PCV on the other side of the bike.
Nobody offers these parts for sale, and I would strongly suggest that nobody try to remove and/or clean this area out, due to the screens being VERY delicate, and directional.
These pictures were provided AFTER a new SMC was installed, and the old one taken apart to see what made it tick.
The small wire inserted into the rear of the cartridge is a very small E string from the lightest set available, and had to be forced into the hole (damaging it) with pliers. The piece sticking out the left of the cartridge is 3 mm of varnish and hardened crap that the string pushed out.
For your safety, just replace the entire unit and move on.