Oberon Slave Cylinder review, (Preliminary.)

Note that this is only a preliminary review and the bike the part was attached to is a huge, steaming, turd.

OK, so first up Michael had to do an air bit of stuffing about to get it to fit and the washers supplied with the kit don't work in this application. That aside the pull is indeed lighter but it is also vague and, at least with the shorty levers on the bike in question, the span adjustment has to be on the furthest out setting to get enough lift for separation and even then there is enough drag to make selecting neutral difficult at a standstill.

Now that may be down to the lever on this bike, it certainly doesn't help, and the clutch has been off at some point and like everything else on the bike may of been the result of butchery on reinstallation. There may also have been bleeding problems, but the pull and feel remains consistent so I think probably not.

All in all, at the moment, I am underwhelmed. But I'll report back after we have re-motored this shitbox it's fitted to and fitted a set of better levers.

So, this is on the White shitter?

Yup. That's why the very large 'Provisional'. When we do the final autopsy on the engine in that POS it's going to be, errrrr? *Interesting*.

Tee hee!

I've seen these advertised and they would seem a good option for those wanting to keep the bike stock (I actually like the stock levers)

My clutch was 28-43k miles old and i got enough lift - no drag at lights & gear selection unchanged.

So i think it should be ok on your 'white shitter'


from what Paul and Beetle said the better leverage of a radial master cylinder would complete the thing

I have also fitted one recently along with a new clutch.

I too have short levers which I have adjusted to max span and still have neutral selection issues, but no drag.

I am going to try the OE clutch lever, if not I may swap back to the large piston Moto Guzzi slave and see if the problem goes (as there isn't a great deal of difference in lever pressure between them)

Considered the Oberon slave, but instead went for a Brembo RCS16 master - best choice ever and a lot easier to install. The radial master allows for setting travel and free movement, something unavailable with the stock master cylinder. It is still sensitive to settings and the combination thereof; I played around a lot to find "the" setting that really suited me.

I have swapped the shorty levers for the OE ones, no real difference in operation selecting neutral from 1st is OK but clunks when going from neutral to 1st.

Will put old slave (command) back on and see if that cures all!

Put the old slave back on and still having issues. Also put on a 13mm clutch master and this hasn't helped either

Brian was that a radial master?

If all the pivot point distances etc were the same 13mm would be heavier than 12mm (by 13squared/12 squared = 17%) and have more lift by the same amount. But the the different distances from pivot point to action on the piston make the same leverage changes as the piston diameters so it all gets very hard to guess.

I don't know why the larger slave cylinder did not give you the same 25-30% reduction in clutch weight i measured -sorry.

It wasn't a radial, it was the same shape as the standard 12mm one - I was hoping that the extra fluid movement would sort out the clunking into gear.

A Brembo RCS16 radial master combined with the stock slave cylinder still delivers that typical "clunk" shifting from neutral to first (especially when cold!), while other gear changes and finding neutral is a breeze. Maybe the Oberon slave with its bigger piston diameter really NEEDS a master cylinder that moves more fluid? If so stepping up from an axial 12 mm to 13 mm might not be enough.

you've got me on the edge of my seat with this. Has there been a consensus on the Oberon cylinder's value with stock levers?

Robeartato wrote:

you've got me on the edge of my seat with this. Has there been a consensus on the Oberon cylinder's value with stock levers?

I´m not an engineer, let alone a master of hydraulics. I´d be interested as well if someone with special experience could chime in on this topic. I just can report my findings.

OK, we’ll my experience with the Oberon device is very limited but the story was I fitted one to the white GRiSO I recently sold. It was a bit of a chore and when we first fired the bike up it was obvious that the bottom end was buggered. The few short rides I took on it in that state the clutch master seemed a bit *Odd* in its behaviour. On reflection though I think that was likely because the crank thrust face had probably work, (We haven’t torn that motor down yet.).

So we swapped out the motor from the ‘Stat write off’ bike into the white one and once that was done I rode it a few times and to my mind, yes, I’d did lighten the pull, but not hugely, and this was offset by the fact that it effectively meant that the span adjuster on the lever became redundant! The only way you could get enough lift to prevent the clutch from dragging was to have the lever set at its widest span.

So. Yes, there is a benefit although it isn’t huge. But a downside as well. I do have another one which I intend to fit to my bike the next time I have the swingarm out but the ‘wide Span’ issue doesn’t worry me. For the ‘Tiny Hands’ brigade it might be more of an issue.

The white bike was sold into Western Australia and the owner is very happy with it. He hasn’t mentioned the clutch pull to me so there’s that. (Shrug?)

Oh, and one other thing, getting the hoses to fit and work was, according to Michael, a bit of an embuggerance.