Getting to Know the Bike

[Andrew Shadow]

I just wonder why people don't try fixing it (rather than replacing) as the only thing different than a regular MC

I will hazard a guess that you were not having any rear brake dragging issues, or at least not having any that were attributable to the SMC, before performing this overhaul. For the benefit of us all, I am curious to know if this is the case. If so, this would explain why your SMC is in such good shape. If you had been experiencing brake problems that are directly attributable to the SMC, there is a very good chance that your SMC would not be in such good shape and would be less likely to be a candidate for a successful overhaul. Most of the successful SMC overhauls that I am aware of were overhauls that were conducted as preventative maintenance. Overhauls that were performed because there was an actual SMC problem have mostly not been successful in the long term.

Many people who were experiencing brake dragging as a result of a problem SMC have rebuilt them only to have them fail again in the not to distant future. This is because the SMC is physically damaged, not just suffering from restricted fluid movement, and is not repairable. The two most common reasons of failure that have been found are;
1- Moisture has settled in the SMC and the piston bore has become the victim of corrosion and is pitted rendering it unusable. This condition is visually apparent.
2- The piston bore is worn oval. This condition allows the piston to caulk sideways in the bore and jam in the applied position when forced there by the hydraulic pressure. Because it is jammed it can not release the pressure. The bore is not necessarily oval to the point that it is easily discernable by eye, so it might get missed during a cursory visual inspection making this defect a little more sinister. It is oval enough to allow the piston to caulk and jam when subjected to the force of the brake hydraulic pressure.

Your SMC does not appear to have suffered from either of these defects, so everything bodes well for a successful overhaul. Come back here and let us know how everything worked out after you have some time and miles on it.

 

[Sadlsor]

Andrew gave the same answers to the question as I would have.
(See Larry? I sometimes DO pay attention!)
Fact is, this problem is common with most of the 1300s that have been left sitting for a few years. At this point, with all of the superb documentation and Articles by @jfheath and @Igofar along with all the SMC discussion threads which appear regularly, I don't know that any new information can be added. Could be wrong.
Not that the mighty ST1300 never has any other issues ever, but this SMC appears to be the only Achilles heel in this superb platform.
And of course, if we adequately and periodically care for these machines, to include regular clutch and brake flush and bleed, most will never have to bother with the SMC as a component.

 

[GitSum]

I cleaned my SMC also, but in the end, I decided to replace it. A brand new one from WebBikeWorld (Japan) was $112, including shipping, and I decided to buy one while they were still available. No regrets

 

[draser]

I will hazard a guess that you were not having any rear brake dragging issues, or at least not having any that were attributable to the SMC, before performing this overhaul. For the benefit of us all, I am curious to know if this is the case.

Well, on my last ride attempt home (initially, I stored the bike in my friend's garage and have had two short rides around his house - no brake locking issues) after rolling the bike outside garage I find myself unable to move it as the rear brake seemed locked. Playing with the brake pedal seemed to unlock it.

 

[Igofar]

Standing by the white courtesy phone.

 

[draser]

Fork service (while waiting on parts): drained the fork(s), right one almost empty (I was expecting that as right side was all oily, left one had some oil in it, oil is properly disgusting:



Upon opening the tubes, some rust can be seen in the right tube, nothing major however.

The sider/tube bushings are intact - teflon is perfect - so they stay. One thing I noticed, different from the manual, the springs have the tapered end down, manual says up. Interesting...

 

[Igofar]

There have been at least 3 misprints in the Honda Service Manual concerning the direction of the springs.
The Narrow end has to be down to sit on the shelf of the cartridge.
Honda simply instructed folks to put the tapered end down, and folks didn't know which end was tapered etc.
Was it tapered getting larger, or tapered getting smaller?
The service manual finally indicated with pictures, of which end they are calling tapered.

 

[draser]

1- Moisture has settled in the SMC and the piston bore has become the victim of corrosion and is pitted rendering it unusable. This condition is visually apparent.

Few comments here, a) this condition will (more than likely) prevent building up pressure, thus the rear caliper may be activated at a lesser rate (if at all) which will affect the "linked brakes" feature; b) I've cleaned and honed MC for my Magnas that were full of corrosion and one of them is actually installed on my 82 Magna (clutch side). This is unlikely to create the "brake dragging" condition for the reasons explained.

I feel I need to add some detail to the portion of the post describing the SMC reassembling. As described in other articles, it is important that the SMC piston moves freely in the bore and fully returns after actuation (otherwise it may block the return port and cause rear brake issues). No significant force needs to be used when inserting the piston back into the bore. The bore needs to be coated in brake fluid and so do the piston seals. After assembly there's no play in the hemi-spherical joint of the piston arm (the piston is fully returned). When exercising the piston it feels smooth and returns back every time.

My final test was to pull sideways on the fork the fork and ensure the fork returns back to straight (doesn't flop around) after release:

Fork pulled sideways:



Fork released (my thumb is actually resting on the paper towel):

 

[Andrew Shadow]

Few comments here, a) this condition will (more than likely) prevent building up pressure, thus the rear caliper may be activated at a lesser rate (if at all) which will affect the "linked brakes" feature; b) I've cleaned and honed MC for my Magnas that were full of corrosion and one of them is actually installed on my 82 Magna (clutch side). This is unlikely to create the "brake dragging" condition for the reasons explained.

I wasn't referring to minor repairable surface corrosion damage. I meant corrosion that isn't repairable, results in the piston jamming, and causes the rear wheel to drag.

 

[draser]

Bike's all together, forks went back on, new wheel seals, torqued front to spec and sequence. Rolled bike around, smooth as butter and no pad noise (lazy calipers) - I'll call it good. Activated both brakes, work as they should. Lots of orange fluid come out during the bleeding - plan on second bleeding after I put some miles on it.



Now dealing with minor electrical issues:

1 - pinch splicer was used for the cruise, upon removal (electrical clean-up) I got this:



2 - Then I have this corroded connector which I have to deconstruct and clean:



Trying to correct this and get the bike started for a test drive - curious how the clutch works. And I guess I'll do a throttle sync check while I have the air box removed.

Last parts needed are the rear caliper bracket and locator clip, and miscellaneous fairing fasteners. Getting there...

 

[GitSum]

2 - Then I have this corroded connector which I have to deconstruct and clean:

View attachment 334440

Last parts needed are the rear caliper bracket and locator clip, and miscellaneous fairing fasteners. Getting there...

Is that connector on the cable to the ignition switch? (if so, a new connector with pins is probably around $10 shipped)

Where can I get this electrical connector? | Electronics / Electrical

Does anyone know where I can get this electrical connector? It's a female, 4 pin - what you would find at the end of the ignition switch. The previous owner of my 2012 ST installed a keyless ignition - Digital Guard Dawg. It looks like they do not make a specific 'plug and play' type kit for...

www.st-owners.com

 

[draser]

Is that connector on the cable to the ignition switch? (if so, a new connector with pins is probably around $10 shipped)

I'll check, meantime I took it apart - below - and cleaned the terminals:



And the clean connector (male shown, female cleaned as well):



Finally, a quick check for throttle sync and minute adjustments to cyls 2-4:



And the airbox went back on and went for a short ride to check clutch/brakes operation, all good. Happy so far. Planning to do a compression test tomorrow and check spark plug condition. Bike's running smooth. Need to inventory the fairing fasteners and order missing ones.

 

[draser]

Today I installed the upper cowl and gauges, missing a lot of push pins - making a list. Performed a quick compression test, as expected I have 172/174/168/172 for cylinders 1 through 4, happy with that. While having the engine running I measured 14.1VDC on the battery for the charging circuit. The spark plugs look new.