Brake fluid fill/bleed help

[4INer]

I evacuated the old fluid from the system on my 05 1300A, rebuilt the SMC, and reassembled. Today while filling the system using an air vac system (plan on using a motion pro for final bleed tomorrow if it comes in), I could not get any fluid draw from the pcv during step 3 ( with left caliper removed and the SMC at 15 deg) or the rear brake caliper rear bleed valve unless I pumped the rear brake pedal. Is this normal? After finishing the bleed everything is working including the SMC, but front brakes are spongy. Hope a final bleed tomorrow fixes that

 

[jfheath]

No, thats not normal. It should pull through quite easily from the rear reservoir At the PCV valve. How does it draw the fluid at the front left lower bleed valve ? That is in the same circuit just before the SMC.
When you rebuilt the smc, did you by any chance take out the small plastic cylinder with two gauze filters on it?

One possibility is that it might be in the wrong way round.





See the pics and full size version of this diagram in post #1 here:

Article [13] - ST1300 - Maintenance - Photos of dismantled SMC | ST1300 Articles

A faulty SMC, taken apart, sawn lengthways, with labelled photos and a commentary. This SMC had a brand new service kit fitted not long before it failed again. A while ago I posted a query concerning some weird behaviour on a friends braking system. The symptoms were that in spite of getting...

www.st-owners.com

Another possibilty is that the SMC piston has been inserted incorrectly - so that the primary seal has inverted itself. It has to go in with the flared end first - which takes some gentle manipulation. If you don't get the wide open end of the seal eased into the bore before pushing it in, it will turn inside out - which will block the flow of fluid through the SMC to the PCV valve.

Third possibility. Did you put PTFE tape on the bleed valve threads ? You have to be careful not to cover the hole just after the end of the thread and before the tapered end. That might be blocking suction, and probably better explains why the brake pedal.can push the fluid through.

 

[dduelin]

My experience with a MityVac was the long circuits fed from the rear reservoir did need help by pumping the brake pedal. The last few years I maintained my ST I quit using a vacuum pump on the rear-fed circuits and just pumped the flush and bleed manually with the pedal.

The front brake circuits from the hand lever are short and should be easily bled manually to a firm lever.

 

[4INer]

No, thats not normal. It should pull through quite easily from the rear reservoir At the PCV valve. How does it draw the fluid at the front left lower bleed valve ? That is in the same circuit just before the SMC.
When you rebuilt the smc, did you by any chance take out the small plastic cylinder with two gauze filters on it?

One possibility is that it might be in the wrong way round.

View attachment 257967

See the pics and full size version of this diagram in post #1 here:

Article [13] - ST1300 - Maintenance - Photos of dismantled SMC | ST1300 Articles

A faulty SMC, taken apart, sawn lengthways, with labelled photos and a commentary. This SMC had a brand new service kit fitted not long before it failed again. A while ago I posted a query concerning some weird behaviour on a friends braking system. The symptoms were that in spite of getting...

www.st-owners.com

Another possibilty is that the SMC piston has been inserted incorrectly - so that the primary seal has inverted itself. It has to go in with the flared end first - which takes some gentle manipulation. If you don't get the wide open end of the seal eased into the bore before pushing it in, it will turn inside out - which will block the flow of fluid through the SMC to the PCV valve.

Third possibility. Did you put PTFE tape on the bleed valve threads ? You have to be careful not to cover the hole just after the end of the thread and before the tapered end. That might be blocking suction, and probably better explains why the brake pedal.can push the fluid through.

pretty sure the piston is in correctly. Lubed it with brake fluid and it went in without reversing the cups and seemed to function smoothly after putting the snap ring back in. But I did use pressurized air to push the old cylinder out and blew the plastic cylinder in the process. I may have put it in backwards. Is the cup sid in or out? Left lower drew normally

 

[Igofar]

pretty sure the piston is in correctly. Lubed it with brake fluid and it went in without reversing the cups and seemed to function smoothly after putting the snap ring back in. But I did use pressurized air to push the old cylinder out and blew the plastic cylinder in the process. I may have put it in backwards. Is the cup sid in or out? Left lower drew normally

Somebody wasn't paying attention in class
Did you damage the screen(s) or O-ring?

 

[jfheath]

That is good information. Sounds like it is not the piston.
Fluid coming through to the front left centre piston (lower bleed valve) means that the line from the reservoir , through the delay valve to the SMC is Ok.

There's a 50-50 chance the plastic cylindrical one way valve is in the wrong way. The symptoms fit. But it's something that you need to be sure about.......

The plastic cylinder (one way valve) goes into the SMC with the blue side facing down towards the cylinder/piston. The diagram shows the O ring resting on top.
It would be prudent to clean out the tiny compensation in the SMC alloy before putting this back in (Primus stove jet pricker / fine top E steel guitar string / single strand of low voltage electrical wire). You probably did this already. Dont try to take out the cartridge from above, unless it simply taps out. You will possibly damage it and there is no replacement part available. There never has been as far as I know.



This is the face that you should be able to see:



This is a photo I took immediately after undoing the two bolts and pulling off the black inlet port.
Note the black O ring that forms a seal with the black inlet port.



The black inlet port bolts down on top of that.
Shown here on a brand new SMC with the white protective plug still in place.

 

[larryg]

This is all very interesting & informative,
but it reinforces my belief in replacing, rather than rebuilding an SMC.
Which I did last year.....

 

[SMSW]

@Igofar has said in other posts that more often than not, attempting to rebuild an SMC ends in failure, and he recommends replacement, like what @larryg echoed. He must be mellowing in his old age because he did not say 'I told you so'.

 

[4INer]

Somebody wasn't paying attention in class
Did you damage the screen(s) or O-ring?

Pretty sure the screens are fine i really didn't want to re-use the o-ring (it had a tiny nick in it) but it was all I had. At this point, the scoot is going back under cover in the shop. I've got three days to get ready for a 4 month long RV trip, and to get both my place and my folks place hurricane prepped incase we get a big blow while we're away. Once thats done, I'll try to get back to the bike before we leave if I have any time, (but even if I do, it's not going to get finished until we return in November. I'll get 'er done after we get back home. Gonna see if I can order a new o-ring so I have it. Twas getting in a bit of a hurry to get everything done with some time left over for several test rides before we headed out (thinking I could fly back down here and ride it up north).........dumb!! Obvious to me now that's not going to happen.........might just order the assembly. How do I know if I need a G01, G02, or G03?

 

[Igofar]

@Igofar has said in other posts that more often than not, attempting to rebuild an SMC ends in failure, and he recommends replacement, like what @larryg echoed. He must be mellowing in his old age because he did not say 'I told you so'.

I told him so

 

[Igofar]

Pretty sure the screens are fine i really didn't want to re-use the o-ring (it had a tiny nick in it) but it was all I had. At this point, the scoot is going back under cover in the shop. I've got three days to get ready for a 4 month long RV trip, and to get both my place and my folks place hurricane prepped incase we get a big blow while we're away. Once thats done, I'll try to get back to the bike before we leave if I have any time, (but even if I do, it's not going to get finished until we return in November. I'll get 'er done after we get back home. Gonna see if I can order a new o-ring so I have it. Twas getting in a bit of a hurry to get everything done with some time left over for several test rides before we headed out (thinking I could fly back down here and ride it up north).........dumb!! Obvious to me now that's not going to happen.........might just order the assembly. How do I know if I need a G01, G02, or G03?

You will not be able to order or replace the O-ring with the correct Honda part as they are not available.
Replace the entire unit as an assembly.....like I told you

 

[jfheath]

The G01, G02, G03 will all fit if the first two parts of the number are the same.
Some sites that you visit might give correct information but not very helpful and say that 06454-MCS-G02 is no longer available. Others are more helpful and list the updated part 06454-MCS-G03. But you may have to load up the details for a later model ST1300 (up to 2007) to find a G03 listed. The same part number was used on all models up to 2007.

From 2008 the model number changed to 06454-MCS-R01 - and these are not interchangeable with the earlier models.

 

[dduelin]

The G01, G02, G03 will all fit if the first two parts of the number are the same.
Some sites that you visit might give correct information but not very helpful and say that 06454-MCS-G02 is no longer available. Others are more helpful and list the updated part 06454-MCS-G03. But you may have to load up the details for a later model ST1300 (up to 2007) to find a G03 listed. The same part number was used on all models up to 2007.

From 2008 the model number changed to 06454-MCS-R01 - and these are not interchangeable with the earlier models.

The correct part number for 2008 and later is now 06454-MCS-R02. Not that it matters for the 2005 in this thread but just for general information of those owning 2008 or later models.

 

[ST-Traveler]

Pretty sure the screens are fine i really didn't want to re-use the o-ring

Better off to call Igofar and get it straightened out.

 

[4INer]

@Igofar has said in other posts that more often than not, attempting to rebuild an SMC ends in failure, and he recommends replacement, like what @larryg echoed. He must be mellowing in his old age because he did not say 'I told you so'.

He did.... lol. A couple of times.....