Brake reservoir' gasket leaks, alternatives?
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Brake reservoir' gasket leaks, alternatives?
04 Dec 2009 13:28
The crusty buildup around the reservoir gasket race on the rear brake master cylinder was so thick that (after cleaning) when I put the old rubber O-ring back in it no longer filled the gap. Now it leaks/seeps fluid.
The master cylinder is rebuilt and works strong.
I am going to look at a plumbing hardware store for an O-ring that might fit.
Is using caulking/gasket sealer/silicon... an option? Worst case scenario is that I may need to go and get another master cylinder from a junkyard if I ever really need to pull the reservoir cup again...
Any thoughts on ways to cure the leak at the reservoir to master cylinder joining other than to find a rebuild kit?
The master cylinder is rebuilt and works strong.
I am going to look at a plumbing hardware store for an O-ring that might fit.
Is using caulking/gasket sealer/silicon... an option? Worst case scenario is that I may need to go and get another master cylinder from a junkyard if I ever really need to pull the reservoir cup again...
Any thoughts on ways to cure the leak at the reservoir to master cylinder joining other than to find a rebuild kit?
77 KZ 650 C1.
77 KZ 650 C1.
Crashed-Repaired, Pods, Kerker pipe, re-wired core bundle, lamp upgraded, homemade rectifier, solid state regulator , Dyna-s ignition, repainted, slightly modified, year-round commuter
Honda Metro 85 mpg Scooter. Dont laugh I will throw it at you
77 KZ 650 C1.
Crashed-Repaired, Pods, Kerker pipe, re-wired core bundle, lamp upgraded, homemade rectifier, solid state regulator , Dyna-s ignition, repainted, slightly modified, year-round commuter
Honda Metro 85 mpg Scooter. Dont laugh I will throw it at you
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Re: Brake reservoir' gasket leaks, alternatives?
04 Dec 2009 13:36
hardware store o rings are going to be geared more towards sealing water,i think you might have better luck at auto parts store

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- Qdude
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Re: Brake reservoir' gasket leaks, alternatives?
04 Dec 2009 15:40
I thought that there was a difference between brake fluid and petroleum based fluids. i.e. The rubber gaskets were damaged by the gasoline, where brake fluid does not degrade the rubber.
Therefore, won't rubber "for water" gaskets also work to seal up a reservoir that holds brake fluid?
I found an O-ring at the hardware store that I think will do the trick, I am going to go and test it on the bench now.
I guess and believe there will be no problems.
Anyone else know differently? I am working with brakes here and am always appreciative of the help.
Quinn
Therefore, won't rubber "for water" gaskets also work to seal up a reservoir that holds brake fluid?
I found an O-ring at the hardware store that I think will do the trick, I am going to go and test it on the bench now.
I guess and believe there will be no problems.
Anyone else know differently? I am working with brakes here and am always appreciative of the help.
Quinn
77 KZ 650 C1.
77 KZ 650 C1.
Crashed-Repaired, Pods, Kerker pipe, re-wired core bundle, lamp upgraded, homemade rectifier, solid state regulator , Dyna-s ignition, repainted, slightly modified, year-round commuter
Honda Metro 85 mpg Scooter. Dont laugh I will throw it at you
77 KZ 650 C1.
Crashed-Repaired, Pods, Kerker pipe, re-wired core bundle, lamp upgraded, homemade rectifier, solid state regulator , Dyna-s ignition, repainted, slightly modified, year-round commuter
Honda Metro 85 mpg Scooter. Dont laugh I will throw it at you
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- gane
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Re: Brake reservoir' gasket leaks, alternatives?
04 Dec 2009 16:15
Qdude, Perhaps I'm missing something.every brake master res.I can think of uses a rubber diaphram to seal brake fluid from cap/and incorperated vent. what's the bike? G
[img][/img] 1977 KZ1000A1
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- TeK9iNe
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Re: Brake reservoir' gasket leaks, alternatives?
04 Dec 2009 17:36 - 04 Dec 2009 17:39
Use DOT 5 brake fluid. It doesn't eat paint and it is compatible with all rubber stuff for sure.
It also has a very high boiling point (less brake fade), and doesnt absorb water as quickly.
Cheers.

PS. DOT 5 is not compatible with any other fluids. Hydraulic system must be completely drained first.
It also has a very high boiling point (less brake fade), and doesnt absorb water as quickly.
Cheers.

PS. DOT 5 is not compatible with any other fluids. Hydraulic system must be completely drained first.
Motorcycle Shop Owner/Operator
79 Kawie Z1000 LTD
81 Kawie Z1000 CSR
83 Honda VT750C A
85 Kawie GPZ900 A2
86 Zukie GS1150 EG
93 Yamie XV1100 E
Lucky to have rolled many old bikes through my doors
79 Kawie Z1000 LTD
81 Kawie Z1000 CSR
83 Honda VT750C A
85 Kawie GPZ900 A2
86 Zukie GS1150 EG
93 Yamie XV1100 E
Lucky to have rolled many old bikes through my doors

Last edit: 04 Dec 2009 17:39 by TeK9iNe.
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Re: Brake reservoir' gasket leaks, alternatives?
04 Dec 2009 20:10
I'd stay away from DOT5. DOT5 brake fluid is not hygroscopic - it doesn't absorb moisture; so the moisture that enters the brake system will "puddle" at the lowest parts of the brake system and cause corrosion. Obviously, some folks here have used DOT5 with good results; maybe they're not in a high humidity environment, who knows. DOT5 has a very high boiling temperature and is often used in non-ABS racing applications, but racers change their brake fluid often thus purging the water. On a KZ650 with stock brakes the difference in boiling point is meaningless as you will never generate enough brake heat in street riding to boil DOT 3 or 4. If you stick with DOT 3 or 4 just be careful not to spill it on your paint. If you do decide to use DOT5 you will need to flush your entire brake system very thoroughly or you will experience compatibility problems, and you should flush and refill at least annually to mitigate the puddling problem. Ed
1977 KZ650-C1 Original Owner - Stock (with additional invisible FIAMM horn)
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Re: Brake reservoir' gasket leaks, alternatives?
04 Dec 2009 21:21 - 04 Dec 2009 21:22
GANE-
If I understand it correctly, rubber is NOT impervious to petroleum. So, don't use rubber for a fuel line, the gas will eat it up.
Brake fluid does not attack the rubber, so it is used on brake systems.
Therefore, I think I am safe using plumbing O-rings as the gasket for the reservoir.
So far the fix works like a charm.
I am going to stick to Dot 3.
just need to bleed the front brakes now to finish the hydraulics.
Oh yeah, 77 kz650c1.
If I understand it correctly, rubber is NOT impervious to petroleum. So, don't use rubber for a fuel line, the gas will eat it up.
Brake fluid does not attack the rubber, so it is used on brake systems.
Therefore, I think I am safe using plumbing O-rings as the gasket for the reservoir.
So far the fix works like a charm.
I am going to stick to Dot 3.
just need to bleed the front brakes now to finish the hydraulics.
Oh yeah, 77 kz650c1.
77 KZ 650 C1.
77 KZ 650 C1.
Crashed-Repaired, Pods, Kerker pipe, re-wired core bundle, lamp upgraded, homemade rectifier, solid state regulator , Dyna-s ignition, repainted, slightly modified, year-round commuter
Honda Metro 85 mpg Scooter. Dont laugh I will throw it at you
77 KZ 650 C1.
Crashed-Repaired, Pods, Kerker pipe, re-wired core bundle, lamp upgraded, homemade rectifier, solid state regulator , Dyna-s ignition, repainted, slightly modified, year-round commuter
Honda Metro 85 mpg Scooter. Dont laugh I will throw it at you
Last edit: 04 Dec 2009 21:22 by Qdude.
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- Patton
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Re: Brake reservoir' gasket leaks, alternatives?
05 Dec 2009 05:54
Qdude wrote:
Does the o-ring in question appear on this diagram?
Good Luck!
[Click on image to enhance view.]
The crusty buildup around the reservoir gasket race on the rear brake master cylinder was so thick that (after cleaning) when I put the old rubber O-ring back in it no longer filled the gap. Now it leaks/seeps fluid.
The master cylinder is rebuilt and works strong.
I am going to look at a plumbing hardware store for an O-ring that might fit.
Is using caulking/gasket sealer/silicon... an option? Worst case scenario is that I may need to go and get another master cylinder from a junkyard if I ever really need to pull the reservoir cup again...
Any thoughts on ways to cure the leak at the reservoir to master cylinder joining other than to find a rebuild kit?

Good Luck!

[Click on image to enhance view.]
1973 Z1
KZ900 LTD
KZ900 LTD
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- RonKZ650
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Re: Brake reservoir' gasket leaks, alternatives?
05 Dec 2009 08:56
Yea, there is no oring, so if there is one there it shouldn't be. #4 in the picture is the diaphram which provides the seal. You'll notice the cap of the master cylinder has a slot to let air get up through the threads into the center of the diapham. This allows the diaphram to drop and rise in the master cylinder to compensate for level changes from brake pad wear ect, and still keep the fluid sealed from moisture. You can't simply seal the cap to the body with no diaphram setup. We've talked about dot5 here many times. It's worked fine for me, but it's dry up here. I do the maintenence strickly by the book though and change the fluid every 25yrs :laugh: I've never had one caliper problem, and only one piston leak on a master cylinder in over 30 yrs.
321,000 miles on KZ's that I can remember. Not going to see any more.
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Re: Brake reservoir' gasket leaks, alternatives?
05 Dec 2009 08:56
o ring under resevoir im thinking

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- gane
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Re: Brake reservoir' gasket leaks, alternatives?
05 Dec 2009 10:21
Ach,I'd forgotten that one, and miss-read as well. Sorry. But throw fuel on the fire,, Brake fluids do react to different rubbers, and in some cases changing from dot 3 to say dot 5 can cause deterioration/swelling. rare, but there. Be cautious using plumbing bits, & keep any eye on. luck G
[img][/img] 1977 KZ1000A1
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Re: Brake reservoir' gasket leaks, alternatives?
05 Dec 2009 12:55
Some reservoirs aren't removable.
Others are removable, with an o-ring underneath.
And some are remote with a hose connection.
Apparently the typical parts diagram fails to show whether or not the reservoir is removable.
As I recall, when looking down into a removable reservoir, two screw heads are visible, which screws hold the reservoir onto the bore portion, with an o-ring sealing the juncture.
As to front master cylinder on large fours, here's a pic and some info from Redline.
redlinecycle.com/Brk%20-%20Trap%20Rsrvr%20O-%20Ring.html
Fwiw, the 1976 KZ900-B1 LTD rear master cylinder doesn't have a removable reservoir.
Good Luck!
Others are removable, with an o-ring underneath.
And some are remote with a hose connection.
Apparently the typical parts diagram fails to show whether or not the reservoir is removable.
As I recall, when looking down into a removable reservoir, two screw heads are visible, which screws hold the reservoir onto the bore portion, with an o-ring sealing the juncture.
As to front master cylinder on large fours, here's a pic and some info from Redline.
redlinecycle.com/Brk%20-%20Trap%20Rsrvr%20O-%20Ring.html
Fwiw, the 1976 KZ900-B1 LTD rear master cylinder doesn't have a removable reservoir.
Good Luck!

1973 Z1
KZ900 LTD
KZ900 LTD
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