Clutch pull

My Brembo clutch RCS is 16mm.

I was thinking something like a 15 but then I thought I'd read somewhere the 19 worked because of a different mechanical advantage. C'est la vie.

Thrown the whole idea in the 'Too Hard' basket for now. I'll revisit it later.

Right now I just want to get the Tenni Shitter pimped up with its touring clobber and pissed off to Queensland for registration. Just waiting for it's new shock to arrive and tossing up whether to get Laurie to go though the forks before it heads north. Once it's registered in Peter's name I'll bring it down south again. It's a good ride from Townsville, about 2,000km by the most direct route but if the WA border opens up I might come back via Perth. I wish those drop pegs would arrive.

I can't go ahead with trialing the Brembo unit right now. As soon as I possibly can I'll try it out.
It's a 19 rcs. Is it likely to work ?

From the pictures the next set that they sent Pete are different.
So this is one pretty definitely a genuine Brembo unit.

If it solves the clutch issue I'll buy a matching front brake master cylinder and
fit black aluminium reservoirs behind my carbon screen running through braided lines to the master cylinders.
I really don't like the reservoirs sitting off the bars.

Mark bought some really neat bar mounted reservoirs to sort that but they were not cheap.
Being a pensioner who picks up odd jobs here and there I'm looking for a cheaper solution.

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Nah, it won't work. It's too large. The pull is much heavier, the exact opposite of what you want. Sorry.

Thays a bummer Pete.

But it does add to my finding that either a smaller clutch pump or a larger command cylinder is the way to reduce clutch pull weight

Well yes. That was always the case. My mistake was not calculating the actual lever ratio and doing some magical thinking about how that would assist with countering the problem.

Put simply, I fucked up! Being human I do that regularly. Thing is I'm happy to wear it rather trying to blame someone else or try and make up some load of old bollocks to excuse my ignorance and mistake.

Onwards and upwards!

Bugger.
It's such a class piece of kit

When I saw your message Pete, I went back to your post with the link to the levers and tried to find 15 ou 16rcs but could find any (didn't look for long). Best I found was 17
5. Are these uncommon sizes?

No. For the RCS 16, Google this: Brembo 110.A263.50

Yeah, Brembo ones are readily available. I think Nissin may do one as well.

It actually makes perfect sense if you think about it for a moment. The clutch only has to move one piston and while it may be slightly larger than a brake caliper piston and does have to move a bit further there are eight brake pistons being moved by a 19mm RCS.

Yeah sorry I was talkin about these Chinese knockouts. But thinking about it, many bikes have a cable actuated clutch so it makes sense that 15rsc is not as widespread as larger brake master cylinders, especially for cheapo copycats.

Thanks for the Brembo ref.

Sorry to kickstart a dead thread - but did Oberon ever get back to us about manufacturing a CARC special?

Would kill for a solution that doesn't cost an arm and a leg...

sideshowbob wrote:

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This must be social media hands

Robeartato wrote:

Sorry to kickstart a dead thread - but did Oberon ever get back to us about manufacturing a CARC special?

Would kill for a solution that doesn't cost an arm and a leg...

No they didn't  - and the 5x rise in energy price for business may have screwed them? hope not....

If they are still around you can buy the Morini 1200 master cylinder I did (above in the thread) but then need to
a) get the last 10-12 mm (check this) of the piston cut down to 25mm diameter 
b) get the command cylinder bleed port that Oberon provide bored and tapped to take a banjo bolt for the remote bleeed pipe.

Sadly got to strip my bike over the nex month so if you want more detailed info about how much the piston is machined plz PM

Interesting development

I reached out to Oberon myself shortly before you gave the bad news, Johnny.

Here's what they said:

------
"...We do not manufacture such a [CARC SPECIAL] cylinder at this time. We intend to – but when is far too early to say other than not for the next 6 months."

"...I will be in our weekly meeting tomorrow and I will be raising the matter as I am beginning to see the request for such clutch slaves becoming more frequent."
------

I'm going to go back to him and ask if we could push for a genuine, designed-for guzzi unit (Going so fa as to suggest tapping for the CARC bikes remote bleed, given your own modification works perfectly )

Either way, perhaps if I go to him with a bit of a show of hands now from anyone here interested in such a solution, it might help get the wheels turning on their end.

Ok i measured it
the last 6.5mm of the Oberon piston is machined down to 24mm diameter
I then used a 4mm cross section viton o ring and a paper gasket and have had no problem or leak over the last year (7000 miles).

Picture below of the modified piston
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Either way, perhaps if I go to him with a bit of a show of hands now from anyone here interested in such a solution, it might help get the wheels turning on their end.

In a perfect would like:cheers:
I would like one

Camphill wrote:

Either way, perhaps if I go to him with a bit of a show of hands now from anyone here interested in such a solution, it might help get the wheels turning on their end.

In a perfect would like:cheers:
I would like one

Noted.
I got another update from him today. I sent him through the suggestions we had (namely tapping for the 10x1mm bleed hose) and he will come back to it once the business has finished their latest project.

If it helps the case, I would be up to buy two

If you have a look there should be 2 part numbers for the command cylinder (slave) for the 1200's, the newer one has the small piston and the older one has a larger piston.

I have swapped to one of these and halved the amount of clutch pull.

The difference is that the piston does not go into the hole that the radial bearing and clutch push rod are, so you have to add extra radial bearing(s) if it does not protrude enough, or longer pushrod.

Interesting, i started off by ordering the latest replacement command cylinder and it was the same diameter as the 24.5mm grimeca already fitted.

As you say s larger piston will reduce clutch pull weight (and lift) and as that is a function of the piston surface area it changes as a square of dimension. That means that if you increase the piston diameter by 20% the surface area increases by 44% and that will reduce the clutch weight at the lever and lift by 44%

I know that the command cylinder for the 1100 4V GRiSO was a wider diameter piston

Part number GU05086330, you can see in photos

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There was a part supercession on the 8V GRiSOs from "978379" to "85220R"

I have been unable to see anyone confirm what the difference between these two parts is. Like Johnny says, when he pulled his original cylinder it was the same diameter as the replacement one he tried.

That is good information Robearto, if the command piston off the 1100 is stepped in to fit in the counter boring in the gearbox, it could be a cheap and easy improvement.


But it may be that the counter boring is wider on the 1100?

I have just fitted a new MG one to my Stelvio and that seems nice and light…I did throw a couple more thrust bearings in as IMO it’s halving the work of the little fella, additional thrust bearing does not effect the actuation rod length - the cylinder finds its own parked position as it has an internal spring.