Clarification on Step #3 of Brake Bleed Procedure

Big_Jim59

Big_Jim59

Site Supporter
Joined
Jul 20, 2024
Messages
241
Age
65
Location
Sherman, Texas
Bike
2006 ST-1300
I am going to attempt to do a brake fluid flush on my ABS ST1300. I am not sure it has ever been done. It all looks pretty straight forward except for step #3

It says in step #3 remove left caliper & tilt up NS Back 15 degrees. (use a wire to hold it) I get that. Then using the proporting valve bleeder, vacuum bleed and pump secondary master cylinder.

Question: Do I need to pump the secondary cylinder (the one on the left brake caliper) while I bleed the proporting valve bleeder or is this pump the rear brake?

I just want to make sure I have this correct. I live in fear of sucking air into the system.

Steps that I have:

1) Left Front Caliper- Top Nipple - Fill from Top Res
2) Right Front Caliper - Top Nipple - Fill from Top Res
3a) Remove left caliper & tilt up NS Back 15 degrees. (use a wire to hold it)
3b) Proporting Valve Bleeder -Vacuum bleed and pump sec master cylinder. - location right side above the head and behind the coil
4) Rear caliper - Center Bleeder - Fill Rear Res
5) Right Front Caliper - Nipple on back of caliper - Fill Rear Res
6) Left Front Caliper- Nipple on back of caliper - Fill Rear Res
7) Rear Caliper - Rear Bleeder - Fill Rear Res
 
Video here

Article [13] - ST1300 - Replacing the brake fluid ST1300 Video | ST1300 Articles

Hi Guys, I replaced the brake fluid on my ST1300 this weekend, and thought others might find it useful. In full disclosure, I don't purge the entire system, prior to refilling it, as I do mine the manual method. Again this is just the way I do it, hopefully someone finds it a useful start...
www.st-owners.com www.st-owners.com
go to 10:03 spot
 
Big_Jim59 said:
I am going to attempt to do a brake fluid flush on my ABS ST1300. I am not sure it has ever been done. It all looks pretty straight forward except for step #3

It says in step #3 remove left caliper & tilt up NS Back 15 degrees. (use a wire to hold it) I get that. Then using the proporting valve bleeder, vacuum bleed and pump secondary master cylinder.

Question: Do I need to pump the secondary cylinder (the one on the left brake caliper) while I bleed the proporting valve bleeder or is this pump the rear brake?

I just want to make sure I have this correct. I live in fear of sucking air into the system.

Steps that I have:

1) Left Front Caliper- Top Nipple - Fill from Top Res
2) Right Front Caliper - Top Nipple - Fill from Top Res
3a) Remove left caliper & tilt up NS Back 15 degrees. (use a wire to hold it)
3b) Proporting Valve Bleeder -Vacuum bleed and pump sec master cylinder. - location right side above the head and behind the coil
4) Rear caliper - Center Bleeder - Fill Rear Res
5) Right Front Caliper - Nipple on back of caliper - Fill Rear Res
6) Left Front Caliper- Nipple on back of caliper - Fill Rear Res
7) Rear Caliper - Rear Bleeder - Fill Rear Res
Click to expand...
A helpful tip. In step 3a after you remove the caliper, put something in between the pads, something of a slightly greater thickness than the rotor. This will prevent them from locking up as you proceed to step 3b.
 
Do Both. The purpose of exercising the SMC is not so much to shift fluid through the system - the brake pedal does that - it is to make sure that the SMC piston is moved for its full stroke to purge all old fluid and the build up of gunge. It also gives you a feel for how smoothly the SMC is operating. That is particularly important in your case as you suspect that it has never had a fluid change.

The brake pedal pushes fluid through the SMC ok, but that doesn't do anything for the stagnant fluid in the SMC behind the fluid inlet port. Normally, the SMC has limited movement. It is a good idea to move the SMC back and forth for its full stroke while the PCV bleed valve is open so that it gets a few full strokes with fresh fluid. This helps to keep the bore clean and prevents a pool of old stagnant fluid forming between the secondary seal and the inlet port. Old fluid is wet and will crystalise. When flushing the brake system, the front lever and rear pedal get to move for their full stroke, so they automatically get cleaned and flushed at each fluid change. Not so the SMC, so you have to do it yourself.

If flow is not what you expect then carefully remove the nipple from the PCV bleed valve body and give a few pedal pumps - having first attached a means of catching the ejected fluid. I had a 'grasping at straws' idea once, and tried this. Out shot a lump of crystalised fluid, that would not get past the bleed valve, presumably dislodged by the SMC being pumped. It shot out like a pellet from a potato gun. Ever since I have always made a point of exercising the SMC for a few full strokes in clean fluid, alternating it with pedal pumps which is much more effective at shifting quantities of fluid.

In addition since you suspect that the fluid is nearly 20 years old, I would check that the pistons are clean and with a bleed valve open, push them in. Then close the bleed valve and pump them out again. Just to make sure that all old fluid is ejected and to get a feel of how easily the pistons move. Take precautions to stop the pistons being pushed out too far.


Download the pdf from post #1 of this link.

Article [13] - ST1300 - Brake Maintenance - Getting all the air out of the brake system | ST1300 Articles

A detailed look at the process of getting the air out of the Honda ST1300 brake lines. A sequence of diagrams of the brake circuits, colour coded to show which parts of the system are being accessed when each bleed valve is opened and explanations of where the trouble spots are. These are just...
www.st-owners.com www.st-owners.com
 
Last edited:
jfheath said:
Do Both. The purpose of exercising the SMC is not so much to shift fluid through the system - the brake pedal does that - it is to make sure that the SMC piston is moved for its full stroke to purge all old fluid and build up if gunge. It als gives you a feel for how smoothly the SMC is operating. That is particularly important in your case as you suspect that it has never had a fluid change.

The brake pedal pushes fluid through the SMC ok, but that doesn't do anything for the stagnant fluid in the SMC behind the fluid inlet port. Normally, the SMC has limited movement. It is a good idea to move the SMC back and forth for its full stroke while the PCV bleed valve is open so that it gets a few full strokes with fresh fluid. This helps to keep the bore clean and prevents a pool of old stagnant fluid forming between the secondary seal and the inlet port. Old fluid is wet and will crystalise. When flushing the brake system, the front lever and rear pedal get to move for their full stroke, so they automatically get cleaned and flushed at each fluid change. Not so the SMC, so you have to do it yourself.

If flow is not what you expect then carefully remove the nipple from the PCV bleed valve body and give a few pedal pumps - having first attached a means of catching the ejected fluid. I had a 'grasping at straws' idea once, and tried this. Out shot a lump of crystalised fluid, that would not get past the bleed valve, presumably dislodged by the SMC being pumped. It shot out like a pellet from a potato gun. Ever since I have always made a point of exercising the SMC for a few full strokes in clean fluid, alternating it with pedal pumps which is much more effective at shifting quantities of fluid.

In addition since you suspect that the fluid is nearly 20 years old, I would check that the pistons are clean and with a bleed valve open, push them in. Then close the bleed valve and pump them out again. Just to make sure that all old fluid is ejected and to get a feel of how easily the pistons move. Take precautions to stop the pistons being pushed out too far.


Download the pdf from post #1 of this link.

Article [13] - ST1300 - Brake Maintenance - Getting all the air out of the brake system | ST1300 Articles

A detailed look at the process of getting the air out of the Honda ST1300 brake lines. A sequence of diagrams of the brake circuits, colour coded to show which parts of the system are being accessed when each bleed valve is opened and explanations of where the trouble spots are. These are just...
www.st-owners.com www.st-owners.com
Click to expand...
Now that's what I am talking about. The SMC works on my bike but I want to do the fluid exchange to keep it so. I also have a bit of sponginess in my rear brake and I want to make sure I have no air in the system.
 
Big_Jim59 said:
Now that's what I am talking about. The SMC works on my bike but I want to do the fluid exchange to keep it so. I also have a bit of sponginess in my rear brake and I want to make sure I have no air in the system.
Click to expand...

I meant to comment on that bit - but forgot. There's nothing wrong with putting in the new and chasing out the old without introducing any air. When I got my first 1100 with ABS/TCS/CBS, I hadn't got a clue about how the brakes worked. So I did exactly the same.

I use the remainder of the bottle that I filled up with last time in order to flush out the old and get rid of as much air as I can. The remainder of that bottle is probably wet, but it will certainly be in better condition than what is in the lines. The I open the new bottle and flush out the old and I go round the cycle a few times with the brand new stuff getting the last few minute bubble, tapping and flexing the hoses. When I say I use the old - I am servicing my brakes every 12-18 months. I always have a brand new 1 litre bottle and I know if I get an awkward bubble int here, I will get through all of that and have none left. What normally happens is that I use up the old, and then end up using less than half of the new - so that gets labelled with when I opened it, and saved for the first flush next time.

When you say that the SMC works - I assume that you have checked that it releases the back brake after it has been applied ?
Yeah, I know. Just checking.
 
You must log in or register to reply here.
Back
Top Bottom