Yep....I'm on it
The dreaded Rear Brake Master Cylinder... I need a replacement. Any ideas?
- Thread starter SKR
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Good point. I was distinctly looking at 43510, so perhaps the G02 assembly is an option after all.
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Hmmm. Everywhere I have looked suggests that there is no difference between the standard and ABS models throughout the range.
Except in 2008 and 2009, the rear brake master cylinder is listed as a 43510-MCS-R01 instead of a 43510-MCS-G01 or G02 for all other models - including the USA 2012 model and the Uk 2014 model.
In the Uk the R01 is showing as back order, no stock. Which means they have to get it from europe or Japan.
Will the G01/G02 version fit ? I don't know. Generally, R01 rather than G01 seems to be more than a minor update. Eg The parts are not compatible between the two, although they may both fit on the same bike if all of the changed parts are fitted.
If the changes to the front braking system in 2008 are indicative, the entire front braking system with the new R01 code will physically fit on the older bikes. Wheels are the same, fork legs are the same. But none of the parts with the R0x revision code are compatible with the G0x parts. Eg the pads are not interchangeable, neither is the brake lever. But with this, there are other issues - the right hand bracket supports a different sensor and the pulsar ring is different, as it the ECU. I'm just saying that it would physically fit.
I checked out the 'Step' - the large silver footrest bracket - onto which the rear master cylinder is mounted. They are the same, so the G01/G02 Master Cylinder will physically mount in the same place. You would need to check the part numbers for anything that connects with the MC - eg brake lines and the reservoir mount and hoses, brake pedal linkage. It would make sense to check your 2008 model against the USA 2012 model which also uses the G02 MC. The Step on the 2008 model is the same as the 2012, but it is different from the Pre-2008 models (The pre 2008 models do not have the rubber grummet to support the plastic side infills.)
It might turn out to be not such a big difference.
When I changed my radiator, there were two versions, one was £100 cheaper than the other. Fortunately David Silver informed me that mine was the cheaper version. Afterwards, I checked the part numbers for everything that came into contact with it. The frame, the hoses, the fan, the cables, the bolts. Everything was identical. Except the radiator cap. The old radiator cap would not fit the new radiator.
You may find that the only parts that are different are all included in the MC sub assembly.
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nb the change in rear master cylinder cannot be to do with the change at the front caliper as the USA 2002 model and the UK 2014 model both reverted back to using the G02 master cylinder - yet they retain the new style front calipers. I don't think the rear calipers have ever changed.
Except in 2008 and 2009, the rear brake master cylinder is listed as a 43510-MCS-R01 instead of a 43510-MCS-G01 or G02 for all other models - including the USA 2012 model and the Uk 2014 model.
In the Uk the R01 is showing as back order, no stock. Which means they have to get it from europe or Japan.
Will the G01/G02 version fit ? I don't know. Generally, R01 rather than G01 seems to be more than a minor update. Eg The parts are not compatible between the two, although they may both fit on the same bike if all of the changed parts are fitted.
If the changes to the front braking system in 2008 are indicative, the entire front braking system with the new R01 code will physically fit on the older bikes. Wheels are the same, fork legs are the same. But none of the parts with the R0x revision code are compatible with the G0x parts. Eg the pads are not interchangeable, neither is the brake lever. But with this, there are other issues - the right hand bracket supports a different sensor and the pulsar ring is different, as it the ECU. I'm just saying that it would physically fit.
I checked out the 'Step' - the large silver footrest bracket - onto which the rear master cylinder is mounted. They are the same, so the G01/G02 Master Cylinder will physically mount in the same place. You would need to check the part numbers for anything that connects with the MC - eg brake lines and the reservoir mount and hoses, brake pedal linkage. It would make sense to check your 2008 model against the USA 2012 model which also uses the G02 MC. The Step on the 2008 model is the same as the 2012, but it is different from the Pre-2008 models (The pre 2008 models do not have the rubber grummet to support the plastic side infills.)
It might turn out to be not such a big difference.
When I changed my radiator, there were two versions, one was £100 cheaper than the other. Fortunately David Silver informed me that mine was the cheaper version. Afterwards, I checked the part numbers for everything that came into contact with it. The frame, the hoses, the fan, the cables, the bolts. Everything was identical. Except the radiator cap. The old radiator cap would not fit the new radiator.
You may find that the only parts that are different are all included in the MC sub assembly.
-----
nb the change in rear master cylinder cannot be to do with the change at the front caliper as the USA 2002 model and the UK 2014 model both reverted back to using the G02 master cylinder - yet they retain the new style front calipers. I don't think the rear calipers have ever changed.
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John, thanks so much for all of the details here. Following your logic, I looked at the differences in other part numbers between the models. Sure enough, take a look at a 2007 versus a 2008 - specifically (3) Connector and (7) Hose. Both connect to the RMC. The hose is a 'controlled part', not sure what that means. There are other parts that are different as well. That scares me when it comes to G02. Looks like the same thing on the 2012+ as well.
www.partzilla.com
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Honda Motorcycle 2007 OEM Parts Diagram for REAR BRAKE MASTER CYLINDER (ST1300) | Partzilla.com
Buy OEM Parts for Honda Motorcycle 2007 REAR BRAKE MASTER CYLINDER (ST1300) Diagram
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Honda Motorcycle 2008 OEM Parts Diagram for REAR BRAKE MASTER CYLINDER (ST1300) | Partzilla.com
Buy OEM Parts for Honda Motorcycle 2008 REAR BRAKE MASTER CYLINDER (ST1300) Diagram
www.partzilla.com
- Joined
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Glad that was useful. I have just this second finished comparing the 2009 model (basically the same as the 2008) with the UK 2014. I thought it would be useful for you to have a check - and I was curious to know for future reference.
For anyone else looking in, the 2008 model specifies the 43510-MCS-R01 Master Cylinder, whereas the 2014 (UK) and 2012 (USA) revert back to the 43510-MCS-G02. But the hoses/clamps seem to be different.
The parts that are different from my research are:
The Master Cylinder Assembly
The Connector on the MC for the hose (which comes as part of the master Cylinder Assembly.
The hose which connects the reservoir to the Master Cylinder
The two clips that clamp the hose at each end.
The service kit for both master cylinders is the same.
The reservoir is the same.
My gut feeling is that the MC itself hasn't changed at all. It is just the way that the hose is connected to it that has changed. All other parts that make up the assembly are the same (on the UK fiches).
So I reckon that the G02 model could be used to replace the R01 model. They do seem to have fiddled around with the hose, clamps and the inlet port connector. So whichever you go for, the inlet port connector comes with the MC, so you would need the hose and both clamps for that version. I would, if possible go for whatever is listed for the USA 2012 model. That (I think) is the latest modification - we had one in 2014, but I think supply had dried up over there before our supply did.
For anyone else looking in, the 2008 model specifies the 43510-MCS-R01 Master Cylinder, whereas the 2014 (UK) and 2012 (USA) revert back to the 43510-MCS-G02. But the hoses/clamps seem to be different.
The parts that are different from my research are:
The Master Cylinder Assembly
The Connector on the MC for the hose (which comes as part of the master Cylinder Assembly.
The hose which connects the reservoir to the Master Cylinder
The two clips that clamp the hose at each end.
The service kit for both master cylinders is the same.
The reservoir is the same.
My gut feeling is that the MC itself hasn't changed at all. It is just the way that the hose is connected to it that has changed. All other parts that make up the assembly are the same (on the UK fiches).
So I reckon that the G02 model could be used to replace the R01 model. They do seem to have fiddled around with the hose, clamps and the inlet port connector. So whichever you go for, the inlet port connector comes with the MC, so you would need the hose and both clamps for that version. I would, if possible go for whatever is listed for the USA 2012 model. That (I think) is the latest modification - we had one in 2014, but I think supply had dried up over there before our supply did.
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Excellent work. I can't even get any vendor - who actually has, not just say they have - to sell me an R01 model. So this might be the experiment that figures it out... whether the RMC is actually causing my issues or not is another story. Igofar and I have chatted about that, he feels it is likely not. The shop is willing to refund me if it doesn't work though, so I'm willing to try. It'll be a few days before I can touch the bike regardless.
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When I read your initial info, I didn't think it would be the rear master cylinder. My suspicion was that the SMC was not cylindrical - you get the impression that air has got in to the rear circuit. But it hasn't. The damaged 'oval' bore allows fluid to pass when it shouldn't so the first press of the pedal is spongey. But you have replaced it.
The first time I ever bled the 1300, it took absolutely ages - 3 days - to get the air out of the system. Even then, it wasn't perfect. If you don't know how to get rid of the air, then it just sits there laughing at your attempts. If you think that they are having difficulty at the garage, feel free to print off my article: ST1300 - Getting all of the air out of the Brake System - and give them a copy. There are a few garages around here that I know have used it - they never really understood how the combined braking system worked until they saw that. It's on about the 4th page of the ST1300 articles at the moment. But Larry is on the case, he will have told you much more relevant stuff.
I generally bow out of conversations when I see Larry has picked up the message. There's nothing that I can tell you that he can't do better.
Funny enough, I was just on the phone with them. If they are going to have the bike for a few more days and try G02, I expect them to bleed it again. They say they've done it a dozen times, they say they've held pressure overnight, and no go. I spoke to the guy doing the work and he's worked on these brake systems before, 20+ years of experience, etc. etc. so I don't think experience is the issue. Regardless I gave them this exact article - maybe it's all already known to him, but they printed it anyway. We'll see.
Larry brought up one more excellent point. There was a rear brake hose recall, as I'm sure many are aware. We're talking about a discontinued part, which connects to the rear brake hose, and all of the clamps/hoses have had their part numbers changed in other models...
Doesn't seem like a stretch to say that Honda reverted to an older design for these, but never 'superseded' the R01 part with G02 in the parts system as compatible with the 2008 ST. That seems like a pretty fair guess.
Doesn't seem like a stretch to say that Honda reverted to an older design for these, but never 'superseded' the R01 part with G02 in the parts system as compatible with the 2008 ST. That seems like a pretty fair guess.
Update: Returned home with the ST. Made it a few miles and then the drag returned pulling in to the garage. Front wheel rotates 1.25+ with a gentle push, rear wheel is down to .25 rotations. So, the dealer didn't fix this it all. More to come on that...
The white courtesy phone ringeth however and Igofar has me pursuing some avenues. Seems like maybe it's EBC pads, SMC locked, or the rear axle nut tightened improperly. We'll see! Larry is being very patient dealing with my poor catalog of tools.
The white courtesy phone ringeth however and Igofar has me pursuing some avenues. Seems like maybe it's EBC pads, SMC locked, or the rear axle nut tightened improperly. We'll see! Larry is being very patient dealing with my poor catalog of tools.
With seriously generous assistance from CruSTy and Igofar, I think we can call this one fixed. Replacing the SMC outright appears to have solved things.
I road about 60 miles and while there is a little bit of resistance, the rear brake is releasing pressure properly and not locking up. I'm getting a full rotation out of the rear tire on the center stand, and I suspect both that and some rear brake heat will improve as the OEM pads set.
This forum is the one of the best crowd-sourced resources I've ever experienced. All of you have made a great community here. Larry has probably spent at least 5 hours on the phone with me at this point, and helped diagnose the issue, get parts ordered, and connect me with someone more experienced. Chuck drove to my house, lent me his tools and all of his knowledge, and got this ST moving again. Not a chance I could've repaired this on my own.
I do think maybe there's something to contribute back to the forum here, and that is regarding the rear master cylinder. I believe we confirmed that the 08 (and probably later models) are indeed discontinued and you cannot source them, except maybe from Europe if you're very lucky. Using the same part as the police models does appear to work though and so we're not SOL on that. Ultimately not the issue with my ST, but someone might need to know that if they have an actual issue with their rear master cylinder in the future.
I road about 60 miles and while there is a little bit of resistance, the rear brake is releasing pressure properly and not locking up. I'm getting a full rotation out of the rear tire on the center stand, and I suspect both that and some rear brake heat will improve as the OEM pads set.
This forum is the one of the best crowd-sourced resources I've ever experienced. All of you have made a great community here. Larry has probably spent at least 5 hours on the phone with me at this point, and helped diagnose the issue, get parts ordered, and connect me with someone more experienced. Chuck drove to my house, lent me his tools and all of his knowledge, and got this ST moving again. Not a chance I could've repaired this on my own.
I do think maybe there's something to contribute back to the forum here, and that is regarding the rear master cylinder. I believe we confirmed that the 08 (and probably later models) are indeed discontinued and you cannot source them, except maybe from Europe if you're very lucky. Using the same part as the police models does appear to work though and so we're not SOL on that. Ultimately not the issue with my ST, but someone might need to know that if they have an actual issue with their rear master cylinder in the future.
CYYJ
Michael
I visited David Silver's main site in the UK last year. The place is HUGE, and there is an amazing museum of Honda motorcycles there. Remarkably, they are not a Honda dealer, though they specialize in Honda parts. I believe they buy up NOS (New Old Stock) from all over the world to maintain their inventory.
I highly recommend this company - they know what they are doing, and they are a pleasant bunch of people to deal with.
Michael