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Old April 21st, 2017   #81
echo
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Default Re: Brakes dragging - Possibles causes?

I have to admit, my fans have been pretty great.
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Old 4 Weeks Ago   #82
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Default Re: Brakes dragging - Possibles causes?

Finally, I did install a SMC rebuild kit and flushed the whole brake fluid system according to the procedure in the Honda shop manual.

While performing the flush, I was not convinced it was perfect as there was almost nothing bleeding from the proportioning control valve, you know, the component requiring removal of the right side main fairing. There was "normal" bleeding from the other 6 bleeders.

So at the end of the process, I did the whole sequence of bleeding again. This time there was a bit more fluid bleeding from this valve but not much. The pump pressure was indicating 20 (psi?) and was not dropping while a very small quantity of fluid was bleeding. This was the end of the day and I had enough so I put back all the fairings and went for a short ride. While testing the brakes, I noticed I have a spongy rear brake pedal. I don't really remember, if previously, it was that spongy as I don't use this pedal very often while riding. The front lever is perfect, not spongy at all but I don't really like the rear. I wonder if many ST riders have a spongy rear brake pedal?

Some thoughts on the results;

Positive:

1. I can ride my bike!
2. No more clunking sound from the SCM when going over small bumps or cracks - I really like this!
3. Rear brake caliper dragging is cured I would say 95%

Negative:

1. Spongy rear brake pedal
2. Rear brake still dragging a bit as the disc is always slightly warmer than on the front in normal use. When doing my test, afetr few kms riding without using the brakes, I ride uphill and stop the bike (without using the brakes); front discs are stone cold while rear is a bit warm. Maybe it is normal.

What's next:

I might try to perform the very last step of the bleeding sequence using the conventional method of a second person pumping the pedal and holding it while I open the bleeder. What do you thing, any chance this would help the spongy pedal issue?
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Old 4 Weeks Ago   #83
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Default Re: Brakes dragging - Possibles causes?

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Originally Posted by Dan55 View Post

What do you thing, any chance this would help the spongy pedal issue?
Yes, you still have air in there, re do the step to the PCV valve again with the SMC tipped up. you can work out which way the fluid flows and get the outlet at the top, this ensures any air in there goes upwards. You don't need to pump the SMC, just make sure the air in it is at the highest point to expel it.
Conventional is always best, even with PTFE on bleed screws IMHO its very hard to remove all air with a vacuum of some sort.

Are you sure the rear is actually dragging? Its hard to tell with the shaft drive attached, you can always prise open the pads and try spinning the rear, mine wont go round twice with the drive.
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Last edited by Rob2m; 4 Weeks Ago at 03:43 AM.
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Old 4 Weeks Ago   #84
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Default Re: Brakes dragging - Possibles causes?

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Originally Posted by Rob2m View Post
Yes, you still have air in there, re do the step to the PCV valve again with the SMC tipped up.
As I said, I already did the complete sequence twice. I did the complete process including removing the left caliper, tilt it at 15°, finish the bleeding process, reinstall the left caliper and then start over again.

I may do it again but this time with the help of a friend that will pump the pedal. Maybe this MityVac pump is not so good...
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Old 4 Weeks Ago   #85
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Default Re: Brakes dragging - Possibles causes?

Quote:
Originally Posted by Rob2m View Post
Are you sure the rear is actually dragging?
After few kms riding without using the brakes, I ride uphill and stop the bike (without using the brakes); front discs are stone cold while rear is a bit warm.

There is still some slight drag but nothing to really worry compared to the previous situation (before performing the job).
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Old 4 Weeks Ago   #86
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Default Re: Brakes dragging - Possibles causes?

Quote:
Originally Posted by Dan55 View Post
Finally, I did install a SMC rebuild kit and flushed the whole brake fluid system according to the procedure in the Honda shop manual.

While performing the flush, I was not convinced it was perfect as there was almost nothing bleeding from the proportioning control valve, you know, the component requiring removal of the right side main fairing. There was "normal" bleeding from the other 6 bleeders.

So at the end of the process, I did the whole sequence of bleeding again. This time there was a bit more fluid bleeding from this valve but not much. The pump pressure was indicating 20 (psi?) and was not dropping while a very small quantity of fluid was bleeding. This was the end of the day and I had enough so I put back all the fairings and went for a short ride. While testing the brakes, I noticed I have a spongy rear brake pedal. I don't really remember, if previously, it was that spongy as I don't use this pedal very often while riding. The front lever is perfect, not spongy at all but I don't really like the rear. I wonder if many ST riders have a spongy rear brake pedal?

Some thoughts on the results;

Positive:

1. I can ride my bike!
2. No more clunking sound from the SCM when going over small bumps or cracks - I really like this!
3. Rear brake caliper dragging is cured I would say 95%

Negative:

1. Spongy rear brake pedal
2. Rear brake still dragging a bit as the disc is always slightly warmer than on the front in normal use. When doing my test, afetr few kms riding without using the brakes, I ride uphill and stop the bike (without using the brakes); front discs are stone cold while rear is a bit warm. Maybe it is normal.

What's next:

I might try to perform the very last step of the bleeding sequence using the conventional method of a second person pumping the pedal and holding it while I open the bleeder. What do you thing, any chance this would help the spongy pedal issue?
Neither front lever or rear pedal should be spongy.
Spongy indicates air in the system.
The bleed sequence is critical.
The sequence is in place to remove air from the system.
Skipping steps is not recommended.

The tipping of the Left Front master cylinder is to position the SMC line to the PCV at it's highest point.
It must be done.
Bleed at the Proportional Control Valve (PCV).

The PCV is not the easiest to bleed.
Very little fluid moves at it is all seriously uphill.
This is a critical bleed.
It is what connects the front (SMC) and rear caliper.
Chances are real good the air in your system is here.
If you do employ the two person bleed method this is the place where it will do "the most good".
It will take some time and follow standard bleeding methods of pumping-opening-closing-repeat until you get steady air free flow of fresh clean fluid when the bleed valve is open.

Pure Speculation and My Opinion based on actually doing it both ways follows.
I put "the most good" in quotes because in my opinion this portion of the bleed sequence is what delivered us the recommendation for a "Commercially Available Air Bleed Tool".
It sure works well here.
Speeds it up and makes bleeding a truly one person job on the ST or any vehicle you bleed brakes on.

You have a fair idea as to the time and amount of fluid that is in each line when you bleed the front caliper.
How much are you actually moving through the PVC should give you a fair estimate on how long you will be bleeding at the PVC to remove the old and replace with new, flushing.
Your going to be here a while.

Paul
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Old 3 Weeks Ago   #87
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Default Re: Brakes dragging - Possibles causes?

Next day off, I'll do the whole shebang again. This time with the conventional method...
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Old 3 Weeks Ago   #88
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Default Re: Brakes dragging - Possibles causes?

Quote:
Originally Posted by Dan55 View Post
Next day off, I'll do the whole shebang again. This time with the conventional method...
TBF, it's not a waste of time if you will keep the bike. Side panels can stay on just loosen the rear fasteners and you can get a spanner and tube to the PCV, the rest is fairly simple with practice & practice makes perfect. I reckon I can do mine in less than an hour now.
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Old 3 Weeks Ago   #89
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Default Re: Brakes dragging - Possibles causes?

Quote:
Originally Posted by Rob2m View Post
Side panels can stay on just loosen the rear fasteners and you can get a spanner and tube to the PCV
I will take a look at this shortcut, thanks.
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Old 3 Weeks Ago   #90
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Default Re: Brakes dragging - Possibles causes?

Quote:
Originally Posted by Rob2m View Post
Side panels can stay on just loosen the rear fasteners and you can get a spanner and tube to the PCV
Thanks Rob, this was good advice. I finally did a full bleeding sequence today and everything is fine now. Done it the ol'fashioned way (no MityVac) with a friend of mine helping with pumping the lever and pedal. There was some air left in the system and expelled from the PCV and the rear caliper.

Did the clutch too.

Thanks to all.

Special thanks to Paul and Rob.
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