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Old 03-15-2012, 05:39 PM   #31
gefr
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I am diving into this M/C failure.

I noticed the piston has signs of friction with the cylinder at the deep side, where the return spring is located. That means the hard cylinder bore paint doesn't wear from the friction with the rubber seals, but with the piston. What would ve caused this? bad alignment between the piston and the spring? I believe if there was an oring on the piston, it wouldn't allow the friction between metal, making the m/c longevity longer.
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Old 03-15-2012, 05:50 PM   #32
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Originally Posted by gefr View Post
... What would ve caused this? bad alignment between the piston and the spring? I believe if there was an oring on the piston, it wouldn't allow the friction between metal, making the m/c longevity longer.
I don't know and you are probably right on all accounts.
But by looking deeper into the Design & Materials used.. I decided to replace it and not beat a dead horse.

So far with with over a year of service and about 7000 miles on my alternative replacement, it has been problem free.
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Old 03-18-2012, 11:56 PM   #33
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I think I have an explanation on the cause for m/c failure.

The clutch lever wears at the pivot cylinder and starts operating out of alignment. This causes side forces that weren't taken into account in the design. So the piston starts wearing the bore, the spring also pushes sideways and we end up with premature failing m/c.
Some preventative measures could be the following:
1) lighter fluid than Magura 7,5wt, reducing the forces at the lever. The more resistance the lever gives to the driver, the stronger and more out of alignment he pulls the lever. I would recommend fork oil 2.5wt or 0wt. I have been using it for years with no ill effects
2) Installing needle bearings in the place the lever pivot bushing is located, OD=9mm, ID=6mm
3) Installing ball bearings in the place the red push rod is hinged, OD=8mm, ID=5mm . However here you will need to have a workshop grind the original bushing, from both sides down to 5mm. Sorry I can only email pictures or someone help me out.
That gave me 130k kms problem free miles as far as m/c is concerned.
Cheers.
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Old 12-17-2013, 11:00 AM   #34
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I could resleeve your clutch master cylinder for a fee.

Also install a smaller piston to lighten the feel on your hand. And the sleeve will be made of stainless steel, harder than the Magura aluminum.
You will need to send your master cylinder over here.
That should be an improvement.
Cheers.
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Old 12-17-2013, 01:24 PM   #35
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So with the SS sleeve and smaller piston assy, do you still see the need to use needle bearings?

What size piston are you going down to, can you provide it, and is it a straight swop into the resleeved master, and will the clutch switch still function?
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Old 02-11-2014, 06:44 AM   #36
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I have a master pump that's leaking, for the third time AGAIN!.
I read the whole thread today.
What do you think is the best way to solve this once and for all?
get the SD pump?
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Old 02-11-2014, 08:19 AM   #37
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I vote resleeving.

The piston I chose is the 9.0mm diameter. The needle bearings will add longevity to your clutch lever and pump. If you do not install bearings, a good idea would be to replace the lever, when it develops too much vertical play.
Cheers.
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Old 02-11-2014, 08:25 AM   #38
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I have found that mineral oil, as stock, creates the environment for oxidation in the type of powder forged aluminum that Magura uses in the slave. It would stand to reason that years later, we would begin to see the same thing in the master as its farther from the heat source.

I also have an '06 and switched to synthetic fork oil after my first fluid change. The Magura Blood/mineral oil came out black indicating the presence of aluminum oxide. Since swapping over back in '07, the fluid comes out clear and clean and I haven't had a problem with either the stock slave nor the master.

I agree with gefr above as to the fix, but I'd only proceed that direction if either cylinder gone bad. I particularly like the idea of boring the cylinders out and sleeving with stainless steel. Replace the rings with viton or something similar and I doubt there would ever be a problem again.

Nice install of the radial master btw, that is awesome. Pick up a nice set of handguards that clear and it'll be perfect.
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Old 02-11-2014, 08:58 AM   #39
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Since I already bought an Oberon for the slave cylinder that's gone bad, I think I need a clean solution that will definitely work and last.
I've been told (don't know if it's true) that an aftermarket slave cylinder, such as an Oberon, will get the master cylinder fail at some point.
Could that be correct or not? Does anyone know anything about this?
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Old 02-11-2014, 10:06 AM   #40
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The reason for this.

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Originally Posted by Sporting Wood View Post
I have found that mineral oil, as stock, creates the environment for oxidation in the type of powder forged aluminum that Magura uses in the slave. The slave cylinder however is treated with some kind of hard color. It would stand to reason that years later, we would begin to see the same thing in the master as its farther from the heat source. The master cylinder does not seem to have any similar treatment and according to your theory seems to create the dark liquid mixture we see in the reservoir.
Cheers
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Old 02-11-2014, 11:01 AM   #41
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Cheers
You could be right about that. I never noticed any sort of hard coating inside the slave cylinder though the piston does seem to be coated in something.

I always surmised that the issue was a sort of solvothermic reaction between the powder forged aluminum and mineral oil. These two materials are known to not get along well when the fluid gets warm. As the bore eroded, it would enlarge allowing the piston to get cock-eyed and bind up when the thing got hot. It would either slow leak or the piston would bind and get cracked up by the pressure exerted trying to engage the clutch. For me the swap to a synthetic fork oil make all the difference as no longer do I see any black (aluminum oxide) suspended in the old oil when I do my annual swap out and have had no issues.
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Old 02-12-2014, 12:01 AM   #42
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As I remember, master pump and slave have their own hydraulic circuit and do not exchange liquids. Correct?
If that so, no problem in using other (fork oil) than clutch fluid (magura blood).

Am I making any sense?
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Old 02-12-2014, 01:22 AM   #43
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I think it's one circuit.

Quote:
Originally Posted by okourkoulos View Post
As I remember, master pump and slave have their own hydraulic circuit and do not exchange liquids. Correct?
If that so, no problem in using other (fork oil) than clutch fluid (magura blood).

Am I making any sense?


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Old 02-12-2014, 04:06 AM   #44
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Yes it is one circuit.

The two cylinders communicate, as in school physics 5th grade.

The slave cylinder is coated inside out. I damaged one so I know.
Cheers.
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Old 02-13-2014, 06:47 AM   #45
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Originally Posted by gefr View Post

The slave cylinder is coated inside out. I damaged one so I know.
Cheers.
May have been a change then as my original '06 slave and a spare I bought back then are both manufactured with simple machined bores.
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