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

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Old 02-02-2020, 09:54 PM   #1
The Clockie
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Oberon clutch slave fitment

To make the S4R easier for my Missus to ride, I thought I'd fit an Oberon clutch slave to lighten the pull, like I have on the ST4 and Gran Canyon. The odd thing is that the clutch push-rod sticks out too far for the Oberon to clamp to the cases. The original Ducati slave (with the star-shaped end-plug) fits the rod fine, so it must mean that the outer end of the Oberon has a thicker wall, preventing the piston from retracting enough. They supply a spacer for short push-rods fitted to earlier models that show a projection of the rod less than 30mm but mine sticks out by 39mm!

I've stripped the clutch to see if the plate pack is below the proper thickness but it isn't, and the release bearing is seated OK, so the only answer I can see is that either Oberon has got it wrong for the 996 motor or someone has fitted a longer push-rod. Does this ring any bells?

The simple solution is to cut the rod down and polish the tip, hoping that the hardening is all the way through and not just the skin.

While I'm in the clutch, I've taken the opportunity to do the Quiet Clutch Mod and stop it beating itself to death and frightening the neighbours. I guess people here are familiar with this five-minute fix?

Nick
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Old 02-02-2020, 10:32 PM   #2
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Are you sure there's not already a spacer in your new cylinder? Previous research seems to suggest that your pushrod should be 335mm so you wouldn't need the spacer. I think from memory the cylinder comes from Oberon with the spacer fitted and you had to remove it if you had the longer pushrod.

Also, does your pushrod have the anti-rotation pin? If so, perhaps it's not aligned with the slot in the slave cylinder - that would prevent it from seating properly.

Plenty of pushrod information here:
http://www.ukmonster.co.uk/monster/s...ad.php?t=56050

Regarding the "quiet clutch mod", I assume you mean this one:
http://www.ukmonster.co.uk/monster/s...ad.php?t=56305

http://www.ducati-upnorth.com/forum/...iet-Clutch-Mod
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Old 03-02-2020, 02:52 AM   #3
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Thanks for your reply. The Oberon slave came with a loose spacer, and I've checked with a magnet that there isn't one in the piston already. A loose spacer sounds like a good idea though, from the anti-spin point of view.

No, there is no pin in my pushrod, but I'll measure the length today.

The reason that Ducati slaves and early aftermarket ones failed with black fluid reflux is simply that they used NBR seals which break down in contact with hot hydraulic fluid. Viton seals do not and when makers realised this, the problem stopped. It wasn't down to pistons spinning or chain gunk getting in, just chemical incompatability of the seals.

The Quiet Clutch Mod you link to is my own writeup, borrowed by Ducati-upnorth from the ST2_owners web-site for which I penned it. It works perfectly, maintains new clutches and preserves worn ones almost indefinitely. Many thousands of quieter miles have been had by me and other ST owners, and probably by other Ducati owners who don't relish the sound of something destroying itself unnecessarily!

Cheers,

Nick (not a Ducati newbie, just new to the S4R!)
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Old 03-02-2020, 07:38 AM   #4
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Just a thought: if anyone here is interested in the Quiet Clutch writeup, I can post it here, maybe as a sticky or just under Hints & Tips?

Nick
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Old 03-02-2020, 10:54 AM   #5
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Quote:
Originally Posted by The Clockie View Post
The Oberon slave came with a loose spacer, and I've checked with a magnet that there isn't one in the piston already.
Noted - although the spacer is a non-magnetic stainless steel, so wouldn't show up in your magnet test, even if it had been installed.
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Old 03-02-2020, 11:48 AM   #6
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This sounds a bit odd.
All the Ducati slaves are the same fitment from Oberon, so it begs the question, did they supply a non Ducati one by mistake? or perhaps one for a much later, new generation model which could possibly be different?
I must say that when you briefly showed me the still packaged slave the other weekend, it didn't look familiar... A bit more bulky looking than mine.. It was just a glance though and I know you've used Oberon slaves before.

The fact that you didn't find a pinned rod suggests that maybe the rod is not standard? A length check will soon verify that, but I would recommend fitting a new pinned rod of the correct length over shortening the old one.

The only other thing I can think of that might cause a problem, is inside the top hat on the bearing end of the rod. If there is something in that that shouldn't be, it would push the rod out further. Probably isn't the problem but worth a check as they do get gungy in there, there's also the chance of a previous owner doing something strange in there for whatever reason.
The top hat contains an O-ring that folks often miss, it could be crumpled in the bottom of the top hat.... Possibly?
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Old 03-02-2020, 12:56 PM   #7
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My clutch push-rod is exactly the length Luddite said: 335mm.

The top-hat pusher in the clutch cover bearing is clear and the rod slips past the (Viton) O-ring and seats nicely.

Speaking to Oberon on the 'phone, they confirm that the spacer is not inserted by them. Naturally, the lady I spoke to said they've never encountered such a problem! Steve Street, the Oberon director, said it was a new one to him but subsequently found a thread on Ducati.ms that showed others had had problems too.

https://www.ducati.ms/threads/pushro...ng-for.296561/

I shall look through that and see what conclusions I can draw. Steve recommended buying a new 'correct' pinned push-rod to gain the maximum rod protrusion of 35mm, rather than 39mm that the 335mm rod provides.

We''ll see...

Nick
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Old 03-02-2020, 02:38 PM   #8
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Quote:
Originally Posted by The Clockie View Post
Just a thought: if anyone here is interested in the Quiet Clutch writeup, I can post it here, maybe as a sticky or just under Hints & Tips?

Nick
Hi Nick

If you want to email it to me (along with any copyright info you want adding)
I’ll prepare for an upcoming tech library I’m plotting

cheers
R

ps. Vince, I’ll be in touch with you shortly re. the same thing
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Old 03-02-2020, 05:31 PM   #9
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Nick
Have you been fiddling with the lever end ? and thus resulting in the master cylinder not moving back far enough to release the fluid back into the pot.

When putting the Oberon one on try without the clutch line connected and see ifit seats correctly. beware of fluid squirt.
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Old 03-02-2020, 07:30 PM   #10
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Quote:
Originally Posted by rollo22 View Post
Nick
Have you been fiddling with the lever end ? and thus resulting in the master cylinder not moving back far enough to release the fluid back into the pot.

When putting the Oberon one on try without the clutch line connected and see ifit seats correctly. beware of fluid squirt.
It's not related to the lever end, because the hydraulic pipe is currently unattached from the slave and the system is empty of fluid!

Before I embark on cutting the push-rod down, can anyone advise on which end goes where? One has twin O-rings, the other doesn't. My ST4 workshop manual doesn't show the details but I may be able to find them in the parts list.

Nick
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Old 03-02-2020, 07:40 PM   #11
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The O-rings go to the slave end.
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Old 03-02-2020, 07:43 PM   #12
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Quote:
Originally Posted by The Clockie View Post
Before I embark on cutting the push-rod down, can anyone advise on which end goes where? One has twin O-rings, the other doesn't. My ST4 workshop manual doesn't show the details but I may be able to find them in the parts list.

Nick
The twin o-rings are at the slave cylinder end.

Edit:You beat me to it, Mr Gazza!
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Old 03-02-2020, 08:00 PM   #13
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Thanks Chaps. That the O-rings go at the slave end was indeed shown in the parts list pics on the clutch section of the forum. I'd better check everything is round the right way before I take a cut-off disc to the rod! I can't see any alternative at the moment, apart from buying a new old-style push-rod.

Reading the old threads here, it appears all were mystified by the persistent blackening of the clutch fluid. As I mentioned above, it was the use of NBR rubber in the seals wot dunnit. Even an aftermarket slave from Vee-Two in Oz went the same way but they then upgraded to Viton seals and the problem disappeared.

Nick, getting there slowly...
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Old 04-02-2020, 08:22 PM   #14
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OK, the mystery about the incompatibility of the Oberon slave with my S4R is solved, thankfully before I started hacking the original push-rod down.

The makers suggested I measure the depth and throw of the cylinder, and I compared it with the original Ducati one that does fit and the dimensions were virtually identical. Bemused, I tried it one more time with the clutch fully assembled and realised that the Oberon wasn't seating on the case because the body was fouling the chain. And the reason for that was that whoever assembled it left the screw-in plug on the inner face in the wrong position so the cutaway that should give clearance for the chain didn't do so. What a relief: if I'd gone ahead with shortening the push-rod, it wouldn't have made any difference at all!

When Oberon saw the photo of old and new slaves, they immediately put a new replacement in the post. Steve Street, the director, is a very responsive chap and I commend him and his products, but someone should get a kick up the bum...

Nick
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Old 04-02-2020, 10:06 PM   #15
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I must admit to a secret little sharp intake of breath when you said you had decided to chop the rod. I'm pleased that you got to the bottom of it before the unkind cut..

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.
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