UK Monster Owners Club Forum » .: Technical :. » Engines, Clutch, Gears » Oberon clutch slave fitment

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Old 04-02-2020, 11:28 PM   #16
Flip
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Yes it would be interesting to know when they changed the seal material as my Oberon slave cylinder has always turned the fluid black too- although to be honest I've never been bothered as my bike has the coffin reservoirs so you can't really see it and it doesn't seem to affect the operation of the clutch.

I only really fitted it as it matches the other gold anodised bits on my bike, I don't think it has made an awful lot of difference to the lever pull but I've also never thought the Monster clutch particularly heavy anyway.

It's kind of mid-way with both my little race bike and Vespa P200e's clutches being heavier while my Yammy Thundercat is (a lot) lighter.

Angling the lever(s) so they keep your hands/wrists in line with your forearm makes a bigger difference to ease of use and rider comfort in my opinion.
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Old 05-02-2020, 06:24 AM   #17
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I wouldn't mind a chat with this Steve chappie to see if he can supply seals for my Oberon that will keep the fluid clear.
I was told by a Ducati chap that the black clutch fluid is caused by the rubber seal cap in the reservoir

I changed mine to the clear ones as used on new monster and no black fluid
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Old 05-02-2020, 08:41 AM   #18
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Originally Posted by rollo22 View Post
I was told by a Ducati chap that the black clutch fluid is caused by the rubber seal cap in the reservoir

I changed mine to the clear ones as used on new monster and no black fluid
That might be partly true but its more likely to be the slave seals otherwise wouldn't the brake fluid would turn black too?

I'd still be interested to find out more about these clear reservoir seals you mention.
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Old 05-02-2020, 09:35 AM   #19
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Originally Posted by rollo22 View Post
I was told by a Ducati chap that the black clutch fluid is caused by the rubber seal cap in the reservoir

I changed mine to the clear ones as used on new monster and no black fluid
By which I assume we are talking about the black "rubber" diaphram in the top of the pot? I have the standard round first generation remote pots on mine with custom caps but the original black seal/diaphragms.
I know the pots are of different design, with the brake having two screws in the cap, while the clutch is a screw on cap, so I suppose it's possible that the diaphragms are different materials, otherwise both pots would be affected, as Darren said.. Seems odd though?
The clutch diaphram is much more visible than the brake and produces a flash of black in the translucent pot even if the fluid is clear, so a clear diaphram would help in that respect at least.

I will enquire at Moto Rapido for availability of a clear seal and if I can get one it will part of the pre Weekender service.. My money's on the slave seals though.

Anorak note.. Interesting word; diaphram. It gains a "g" in the plural; diaphragms.
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Old 05-02-2020, 10:48 AM   #20
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So. A quick chat with the ever helpful Craig reveals that they have only ever stocked black diaphagms. There is however an upgrade for the seal, which now takes the form of a rigid translucent plastic ring. This is a tighter fit than the previous and serves to retain the diaphram even in the event of losing the cap, which has happened apparently.

As this sits on top of the diaphram, under the cap, I can see no way that fluid can contact it, so I don't think this has anything to do with the blacking issue at all. Duncan, could you please clarify what part you upgraded and where to source it?

#Always use Extra Virgin fluid.
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Old 05-02-2020, 01:56 PM   #21
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I purchased new complete pots for brake and clutch.Didn't like the cloudy ones.
Sorry for the confusion
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Old 05-02-2020, 09:33 PM   #22
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I asked Oberon's Director, Steve Street, about the seals in his slaves:

"Hi Nick,

We always have, and always will use slightly over spec EPDM Nitrile Rubber.
Our seals are actually machined from frozen material, they are NOT simple O rings like everybody else use. Our seals are purpose made 'U' seals with a carefully designed 'lip' that seals tighter the more pressure that is applied.

The black fluid is often a little misunderstood.
In addition to the cheap O ring that degrades. The original slave body/piston etc is NOT anodised as I am sure you are aware.
Just like when you clean a piece of alloy with polish and a clean cloth, the cloth becomes blackened from the alloy being polished off. The inside of the OEM slave suffers a similar effect. The Oberon Performance unit does not suffer this effect and so the fluid remains clear much longer.
NB; As the original master cylinder suffers the same issue - eventually blackening will still appear as the small piston in the master cylinder pumps back and forth creating the same issue - but over a much longer period of time.

You can confidently report that the Oberon Slave body and seals will practically last for ever... Unless massive use eventually wear's through the anodise (which I cannot imagine will ever happen) the fluid will never blacken unless it is being caused elsewhere, like the master cylinder as mentioned above. Or the slow mixing of any old fluid and residue from the past, remains within the brake lines etc...

To date, we still have 100% non failure of our seals.
After 17 years on the market, I reckon it is safe to say it is a proven remedy.

The wider audience will possibly be interested to hear your conversation. If you do post anything please send me a link.

Kind regards,

Steve Street
Director

Oberon Performance Ltd"

I must say I'm surprised he uses EPDM rubber rather than the more-expensive Viton, because Viton is way better at resisting solvents and has a greater heat tolerance. If I understand him right, the Oberon bore is anodised to resist the generation of black in the fluid from the aluminium being scuffed. Maybe Monster owners with black hydraulic fluid have been using the clutch too much?
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Old 05-02-2020, 09:47 PM   #23
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Thank you for that Nick.
Thank goodness I will be able to sleep soundly tonight, assured that it's not my Oberon slave that's blacking my fluid!

So what are we going to do about the master chaps? As far as I know it's not possible to anodise inside a bore for the same reason that you can't electroplate inside a bore or tube. There is no electrical potential, the electrolyte is only exposed to the polarity of the tube or bore wall. Or am I wrong?

First thoughts are to line the master bore with something. A stainless sleeve perhaps?.. Shouldn't be beyond the wit of man, if a little fiddly!
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Old 06-02-2020, 08:12 AM   #24
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Thank you for that Nick.
Thank goodness I will be able to sleep soundly tonight, assured that it's not my Oberon slave that's blacking my fluid!

So what are we going to do about the master chaps? As far as I know it's not possible to anodise inside a bore for the same reason that you can't electroplate inside a bore or tube. There is no electrical potential, the electrolyte is only exposed to the polarity of the tube or bore wall. Or am I wrong?

First thoughts are to line the master bore with something. A stainless sleeve perhaps?.. Shouldn't be beyond the wit of man, if a little fiddly!
If you did want to pursue lining the master, my good mate Les on the Cagiva Alazzurra forum (Ducati Pantah in drag, for those unaware!) has, I think, done that and made pistons too. I will ask him.

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Old 06-02-2020, 08:28 AM   #25
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There are plenty of reports about darkening of hydraulic fluid but you seldom hear reports of an associated drop off in hydraulic performance.
Maybe a little aluminium oxide in the fluid has no appreciable effect, other than the discolouration.
In which case, perhaps there's no need to fix the "problem".
Regular fluid changes should keep it to a minimum anyway.
If it aint broke .........
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Old 06-02-2020, 08:49 AM   #26
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Thanks again Nick for the offer of a contact. I also have a local pal who has made a series of experimental clutch slaves for the Norton and would be well capable of sleeving a master.
I think it depends how much I allow the black fluid to needle me in the future, as Jeff says, "If it aint broke.. "
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Old 07-02-2020, 08:49 AM   #27
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This could just be my last post on the subject!

I fitted the new Oberon slave last night and bled the system. The lever-pull feels smoother than before and somewhat lighter, being approx 12lbs versus 15lbs by spring-balance measurement. The Quiet Clutch test sequence promises good things too, as the rotary damper function operates in the last few degrees of lever travel. This may alter as the extra friction plate beds down but the audible warning system will alert me! The proof of the pudding will come shortly, but not if the current chilly spell provokes the application of corrosives to the roads again.

Also, a final word from the boss of Oberon that informs about seal material:


"Just a note about the seal materials and our personal findings.
Viton is not as resistant to hydraulic oils, that is why we use EPDM as extensive trials proved to us it did not suffer from swelling or degradation, which we experienced with Nitrile and Viton.

Steve Street
Director
Oberon Performance Ltd"

All good fun!

Nick
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