Front Master Cylinder

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22 Mar 2018 15:07 #780639 by gordone
Front Master Cylinder was created by gordone
I have overhauled my front calipers and replaced the brake lines, the master cylinder was new last year.
Right now can I easy push the brake handle 1/2, after that is harder and on 2/3+ its hard...

What is normal handling of the handle?
I`m feeling it should be harder... right now is identical to what it was before the overhauling...

I don`t know if I expressed me good here? hehe

1981 KZ650-D4, with 1981 z750L engine (Wiensco 810 big bore).

Project:
www.kzrider.com/forum/11-projects/607213...sr-1981-z750l-engine

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  • Scirocco
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22 Mar 2018 16:09 #780641 by Scirocco
Replied by Scirocco on topic Front Master Cylinder
Have you a single disk MC 1/2" (14 mm) or Dual disk MC 5/8" (16 mm)???

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22 Mar 2018 17:02 #780646 by 650ed
Replied by 650ed on topic Front Master Cylinder
Here's an image of the front brake lever on my KZ650-C1 when squeezed extremely tight. Ed


1977 KZ650-C1 Original Owner - Stock (with additional invisible FIAMM horn)
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22 Mar 2018 23:25 #780671 by gordone
Replied by gordone on topic Front Master Cylinder

Scirocco wrote: Have you a single disk MC 1/2" (14 mm) or Dual disk MC 5/8" (16 mm)???


Dual disc.

1981 KZ650-D4, with 1981 z750L engine (Wiensco 810 big bore).

Project:
www.kzrider.com/forum/11-projects/607213...sr-1981-z750l-engine

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23 Mar 2018 00:55 #780672 by Scirocco
Replied by Scirocco on topic Front Master Cylinder
Then you have to bleed a little more air bubbles out of the calipers.
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23 Mar 2018 11:04 #780687 by Z1Driver
Replied by Z1Driver on topic Front Master Cylinder
You might have to bleed the master too. I replaced the Brake Fluid on my C14 (I know different bike all the way around) I use a Mity Vac to remove old fluid which will drain the reservoir quickly if you are not careful which I was not. So I refilled the reservoir keeping a much closer eye on it and bled the calipers till the cows came home. I removed all the bubbies and still had a brake lever as you describe. Sometimes if one ties the brake lever tightly to the grip so the brake is applied over night, air will work it's way out of the little bleed hole in the master. After a night of that, the next day resulted with no difference in the lever. So I punted and bled the master. Ended up with a great brake handle with a ah ha moment.

when I replaced the caliper on the 900, I don't recall having a problem with the system using the Mity Vac. Must have been lucky....Good luck. Tin

Blue 1975 Z1B
Red 2009 Concours 14
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23 Mar 2018 11:50 #780691 by Nessism
Replied by Nessism on topic Front Master Cylinder
You might want to try pumping up the hand lever and then squeezing as hard as you can, then strap the lever back against the grip. The idea is to create as much pressure inside the system as possible so the pistons move closer to the discs. Leave the bike with the lever pulled back for 24 hours and see if the lever firms up.

BTW, did you lubricate the caliper sliding pins with heavy duty black moly caliper grease?
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23 Mar 2018 12:12 #780692 by ajsfirehawk
Replied by ajsfirehawk on topic Front Master Cylinder
Nsssism, I've often heard the process you describe above. When I've heard it before the cap was to be left of the master cylinder reservoir. Cap on or off make any difference?

79 KZ650 SR
80 KZ1000 Z1 Classic
83 KZ1100 LTD
Z900RS
23 Mach 1
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23 Mar 2018 17:20 #780702 by gordone
Replied by gordone on topic Front Master Cylinder

Z1Driver wrote: You might have to bleed the master too. I replaced the Brake Fluid on my C14 (I know different bike all the way around) I use a Mity Vac to remove old fluid which will drain the reservoir quickly if you are not careful which I was not. So I refilled the reservoir keeping a much closer eye on it and bled the

calipers till the cows came home. I removed all the bubbies and still had a brake lever as you describe. Sometimes if one ties the brake lever tightly to the grip so the brake is applied over night, air will work it's way out of the little bleed hole in the master. After a night of that, the next day resulted with no difference in the lever. So I punted and bled the master. Ended up with a great brake handle with a ah ha moment.

when I replaced the caliper on the 900, I don't recall having a problem with the system using the Mity Vac. Must have been lucky....Good luck. Tin


How did you bleed the master cylinder?

1981 KZ650-D4, with 1981 z750L engine (Wiensco 810 big bore).

Project:
www.kzrider.com/forum/11-projects/607213...sr-1981-z750l-engine

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23 Mar 2018 17:21 - 23 Mar 2018 17:22 #780703 by gordone
Replied by gordone on topic Front Master Cylinder

Nessism wrote: You might want to try pumping up the hand lever and then squeezing as hard as you can, then strap the lever back against the grip. The idea is to create as much pressure inside the system as possible so the pistons move closer to the discs. Leave the bike with the lever pulled back for 24 hours and see if the lever firms up.

BTW, did you lubricate the caliper sliding pins with heavy duty black moly caliper grease?


Will try these over the easter.

Yes used brake high temp grease.

1981 KZ650-D4, with 1981 z750L engine (Wiensco 810 big bore).

Project:
www.kzrider.com/forum/11-projects/607213...sr-1981-z750l-engine
Last edit: 23 Mar 2018 17:22 by gordone.

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23 Mar 2018 20:18 #780711 by Nessism
Replied by Nessism on topic Front Master Cylinder

ajsfirehawk wrote: Nsssism, I've often heard the process you describe above. When I've heard it before the cap was to be left of the master cylinder reservoir. Cap on or off make any difference?


Doesn't matter.

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24 Mar 2018 00:42 #780714 by gordone
Replied by gordone on topic Front Master Cylinder

Nessism wrote:

ajsfirehawk wrote: Nsssism, I've often heard the process you describe above. When I've heard it before the cap was to be left of the master cylinder reservoir. Cap on or off make any difference?

Doesn't matter.


If i understand these correct, when you have pressure on the line will the gravity force the air to go up because the weight of the fluid is higher then the air. In therey you will build over pressure in the resvoir by adding air when the cap is on.
But the pressure will have enoufg force to build some over pressure.

1981 KZ650-D4, with 1981 z750L engine (Wiensco 810 big bore).

Project:
www.kzrider.com/forum/11-projects/607213...sr-1981-z750l-engine

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