Clutch pull

Well it doesn't work

The oberon cylinder is tight to fit due to both feed and bleed going to the same banjo-
Original
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Oberon
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But the main problem is that the Moto Guzzi clutch pushrod is pushed by a thrust cylinder which runs in a 26mm bore.
in this pic you can see the thrust cylinder.
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The slave cylinder enters the bore to operate against that thrust cylinder. The original piston is 25mm so there is no problem

The larger Oberon piston hits the back of the housing without lifting the clutch..

So it seems that I am stuck with the 8-10Kg clutch pull

I'm guessing there isn't room to turn up & put a 'thin disc with dimple end' inside to match the OEM piston (or to just extend the pushrod out) ??

Appreciate the update, I still haven't got around to popping down to Oberon with my spare unit - really ought to. from what you have indicated the actual unit bolts on OK, but needs to
match the O ring seal [can't see that on parts diagram] unit to gearbox
Piston needs to match current
bleed need tapping out to banjo size
It may be that they can machine a piston to meet our needs?

The thrust cylinder fits flush to the outer end of the gearcase before it is lifted - so hard to locate an intermediary there.  It is quite large, carries the radial bearing and was probably designed to take side thrust when the clutches used to be cable pulled.

If there is enough demand Oberon say they will machine pistons!!

However The double banjo bolt is so tight to the frame i could not even get 1/12th turn on it - so not possible to tighten it up .

A new feed and bleed hose with a 90 degree double barb banjo to connect to the cylinder in the current position would work. But would add to the expense so that it might be cheaper to get the Brembo radial cylinders anyway.

Thinking about a 2 port cylinder as originally fitted Oberon said that as the bleed drilling is not absolutely perpendicular it would be unlikely to be fluid tight if it was drilled and tapped for the bleed hose. BUT if i can find an engineer to tap the thread and then spot face that surface it could work

Does anyone have a figure for the amount of clutch lift (so I can get the piston machined down) ?

Well I have fitted the Oberon command cylinder (after some additional machining).
The clutch pull has reduced from needing 13Kg pull and 8Kg holding to 10Kg pull and 5Kg holding.
It has exposed how much wasted movement there is at the standard master cylinder

I will give it a try out and ( if it works ) post more details and pictures

things that may not work well
1) is there enough lift for the gearchange now?
2) will gear oil leak out past the command cylinder as the "o" ring clearance has changed.

Any other things i should be looking for?

OK
So originally my 2009 GRiSO Clutch required a force of 12Kg to lift the clutch and  8Kg to hold it in.  I found this very uncomfortable  :    and the amount of effort led me to compromise my riding by avoiding gear changes particularly after a 2-300 mile ride

So I wanted to reduce this force.
When you pull the lever the master cylinder displaces a fixed amount of fluid into the slave cylinder (or as Guzzi call it command cylinder).  It follows that if the command cylinder is wider the piston will be pushed less far than if the command cylinder is narrow. So increasing the bore of the command cylinder (or reducing the bore of the master cylinder) will result in less compression of the clutch spring for the same stroke of the clutch lever and therefore less load at the lever.

Paul chose a very flash master cylinder that presumably has a smaller bore.
As a typically tight Guzzi owner i was after a cheaper solution!
I thought that I could find a cheaper way by getting a command cylinder with a wider bore.  (The obvious risk is that the reduced lift may not be sufficient for the clutch plates to clear and may result in clutch drag).

Well it worked.
I have fitted a modified Oberon CLU-1200 clutch slave cylinder and have now done 100 miles.
I now have a manageable (not light   ) clutch.
The clutch lift force is reduced from 12Kg to 9Kg and the force required to hold the clutch is reduced from  8Kg to 5Kg.  a result

will post the detail below

Details
The GRiSO standard command cylinder has 25mm diameter. The Oberon CLU-1200 command cylinder for the Morini 1200 motor has a 30mm bore oberon CLU-1200 linky.  the mounting screws are in the same place but this part will not just replace the GRiSO part without three key modifications.

(1) bore out the threaded bleed nipple drilling in the CLU-1200 to a 10mm x1mm threaded hole for the GRiSO remote bleed hose banjo.
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(2) Mill down the last 8mm on the operating end of the command piston to 24mm so that it fits inside and does not foul on the 26mm bored hole for the GRiSO clutch thrust cylinder. The pictures shows the difference in bore size and the end of the thrust cylinder boring - i have lost the pic of the reduced diameter piston
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(3) Use a 37mmx5mm od viton ring to seal the clutch command cylinder to the gearbox Viton o ring supplier uik linky  because the Oberon part is narrower external diameter than the standard one.

I feared that the 5mm od o-ring would not seal properly so a friend laser cut a paper washer for the command cylinder – the two together are working - No gearbox oil leaks

Also I used 10mm Dowty O-Rings Bonded Seals (Self Centering Hydraulic Pneumatic washer) instead of the copper washers in case the bored and tapped hole was not perfectly orthogonal to the surface Ebay seller of Dowty washers  .
.

Nice work

Good work. Without feeling it I'd not really be able to judge.

Following this topic though I was ebay surfing a week or so ago and found a ridiculously cheap Chinese 19mm radial clutch master cylinder. I bought it on the spur of the moment, (No, I wasn't drunk! ) but the bike I bought it for, the Written off Shitter, is about to be shipped to Queensland to be re-registered. So I'm going to flick-pass it on to Evans in NZ and he can see if it will help with his lever effort. He's even older and more buggered than me! Hopefully he'll be able to report on whether it works or is a complete waste of money!

I think the original is 15mm bore - can't check without tearing the boot seal.
If so a 19mm will displace 19sq/15sq (361/225) =1.6 times more fluid, so will try to lift the clutch over 1 1/2 times further for the same lever travel.

So i would expect it to be heavier?

Yeah but the lever angles are all different too. As I said, I have no idea if it will assist or make things worse but I thought it worth a try.

Pete Roper wrote:

the lever angles are all different too.

Yes I agree the lever angle complicates the model.
We used to fit smaller MC to Grimeca brakes in the 80s to give more feel but with some brake levers the leverage advantage did not work.

Another complication - if the GRiSO still has a diaphragm clutch spring their spring rate reduces as they are compressed

So you are right it is worth a try - specially a master cylinder as that is much less grief to fit

Pete Roper wrote:

Following this topic though I was ebay surfing a week or so ago and found a ridiculously cheap Chinese 19mm radial clutch master cylinder. I bought it on the spur of the moment, (No, I wasn't drunk! ) but the bike I bought it for, the Written off Shitter, is about to be shipped to Queensland to be re-registered. So I'm going to flick-pass it on to Evans in NZ and he can see if it will help with his lever effort. He's even older and more buggered than me! Hopefully he'll be able to report on whether it works or is a complete waste of money!

Well, the MC arrived. £35.08 delivered to my door. Now it's either genuine or it's such a good copy they even went to the bother of manufacturing a box!

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I'll pop it back in the post to Evans and he can fit it and pass judgement.

Bloody bargain! Good score

I'd love to be able to know for sure whether it's a genuine Brembo. I don't see how it can be unless it's stolen. The fact it comes from China makes me think it's just a very good looking knock off.

Anyway, I've ordered a matching pair from the same company. Brake and clutch. And we'll see what eventuates.

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Just noticed that set are 17.5mm. Silly me. Reordered the right ones......

Pete have you got a gash original to measure the diameter? Looks to me like it has to at least have the boot and bootclip removed before you can see the bore size (and probably the main circlip and puston assy).

Nah, but I believe the 19mm units are the usual 'Go To' for our application. Anyway, I'll have a 17.5 to play with as well because at that price it isn't worth the arse of sending the wrong ones back! I might use the 17.5 brake one on a stock Mana when one comes in, they have smaller pistons. Or a Shiver.

I vaguely remember there was some 'fancy' special hologram on a card that came with or on the packaging, that gives a code you can put on Brembo website.....shows how much attention I paid as I defo don't have it now.....

Found it !.....I think it's a code or QR scan somewhere in the contents/box that you then put into Brembo website & get a certificate to print out.  [You must be registered and logged in to see this image.]

Pete Roper wrote:

I'd love to be able to know for sure whether it's a genuine Brembo. I don't see how it can be unless it's stolen. The fact it comes from China makes me think it's just a very good looking knock off.

Anyway, I've ordered a matching pair from the same company. Brake and clutch. And we'll see what eventuates.

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I would highly appreciate if you could keep us posted on how they work. I'm reluctant to use a chinese knock off on something as important as brakes but if you say they are good I would be willing to try them out. Radial commands for my 1100 sound great.

Are these the 19mm ones that would fit the GRiSO ?
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I fitted RCS19 for Brake and RCS16 for Clutch, both have dial in lever ratio ....these piston diameters work fine

Well, my mistake. The 19mm RCS is far too large! I thought 19mm seemed a bit big but assumed that the lever's mechanical advantage would be different enough to compensate.

Wrong! It requires a 'Gorilla Grip' to move it! Ho hum. Back to the drawing board.