I have recently fitted an Oberon slave cylinder, lovely bit of engineering and wondered if anyone else has fitted on to their 8v 1200’s
If so do you have any thoughts on it?
OK, its got to be said…if you’ve just fitted one, what are your thoughts on it?
Are you not entirely happy with it?
These things are quite popular with Ducati riders, but a few people are unimpressed with the slightly reduced piston travel characteristic of the brand. This is a trade-off for slightly reduced effort to operate the clutch.
I can see how with the Guzzi clutch this could lead to drag.
Any change in piston movement of the clutch slave cylinder will have potentially serious consequences re clutch operation. There is no adjustment system as with the cable operated clutches on older V twins. The hydraulically operated clutches rely on the length of the pushrod to ensure it operates correctly. The Len goth of the pushrod can only be determined by use of a special tool. Moto guzzi then provide a conversion chart which allows the tool measurement to be converted to rod length. The correct rod then has to be purchased and installed. Rod lengths are in 1.5mm increments which suggests that slave piston travel is critical and very little, if any, variation can be tolerated. Has anyone measured the travel of the standard piston and compared it to after market versions? The results would be interesting.
Oberon slaves are excellent I have used them on Ducatis for years. They normally supply the relevant spacers if required for the model supplied. Looks like the dedicated one for the 1200 doesn’t need one. It looks a nice slim design. https://www.oberon-performance.co.uk/moto-guzzi/moto-guzzi-clutch-slave-cylinder
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Has anyone had success with an Oberon slave cylinder on a Moto Guzzi. If so did they have to do work on the clutch push rod or was it a fit and forget job?
I have read your comments and appreciate the replies - a bit of background below
MG large piston p/n GU05086330
MG small piston p/n 85220R was 978739
A long story which involved changing the clutch as the engine was in bits, with the new clutch fitted I also changed my “command” slave cylinder which was a large piston Moto Guzzi one to an Oberon. put in a new pushrod that had adequate length as the original rod was “being” short [see below] (it was also showing wear at both end on the circumference of the rod).
Initially after fitting the Oberon (and being silly I had refitted the swingarm, shock etc) I found that the stepped shoulder was landing on the back of the gearbox, so I needed to either fit a longer pushrod or pack out the “engine bearing set” with another Torrington bearing. weirdly the pushrod (original length) had “settled” and went in further - don’t know why.
Once done I could rotate the prop shaft by hand with the clutch operated - That was promising. So onto road testing, initial testing was not pleasant so added an additional Torrington bearing and this did improve thing a bit, I could now select neutral with a bit of patience.
Now I realise that these are self adjusting by virtue of being fluid filled, I would expect sufficient slave movement to cleanly disengage the clutch and not have to endure clunking into 1st gear. At the moment this is not the case; so I shall be rechecking that there is no air in the clutch circuit (I have left the lever half operated with a cable tie as well) and I also have a master cylinder rebuild kit to fit to see if that is causing issues. I recently re-sleeved the clutch lever pivot as that had worn quite a few thousand miles ago.
The old slave was the large piston Moto Guzzi one and prior to new clutch I could engage (leave a few seconds) and disengage gears without clunking.
So to summarise I am still investigating, the pull is pretty much the same as the large piston slave and I am also wondering if the clutch needs to bed down a bit more as I have only done 700 miles and that might improve matters.
I can “when” it comes to swapping slaves around measure the slave movement between the Oberon and my large piston slave - I did expect a fit and forget as they are similar diameter piston.
A question that I have is both the Moto Guzzi slaves have a spring inside and the Oberon (I haven’t dismantled it) does feel as though it hasn’t got one - does anyone know why the spring is fitted?
Hi Brian, does the spring in the original Moto Guzzi slave cylinder push the piston forward (extended) or backwards (retracted)? Keeping the piston retracted would seem to make sense as it would result in the pushrod being “free” when the clutch is fully engaged. If it keeps the the piston extended then the pushrod would be in contact with the clutch and the piston continuously whilst riding which would result in the domed end of the rod wearing. I’d be interested to know the answer and any other thoughts you may have. The clutch I installed in a colleagues Stelvio worked perfectly from the moment it was installed and required no bedding in. Genuine Moto Guzzi parts were used throughout and the push rod length was set as per the table in the manual after using the special protrusion tool. Cheers Phil
Hi Phil
Both slaves push the piston out because of the spring.
This probably explains the wear on the pushrod
regards
Brian
Thanks Brian. That knocked my thought on the head! Your push rod looks totally different from the one I removed. Ours was in perfect condition. In fact when I replaced the clutch the protrusion gauge indicated that I needed to instal a shorter push rod than the original. I shortened the old one and then formed and polished the domed end. The bike has now covered about 1000 trouble free miles since. We could have done a lot more checking and recording of dimensions when we changed the clutch. If I have another clutch replacement job I’ll certainly do that. Ie slave cylinder piston protrusion at rest, length of push rod, reading from protrusion tool before clutch replacement etc. Cheers Phil
To add to the earlier comment re Ducati fitment; I fitted one to a M750, much lighter lever action and no problems over 7 or 8 years and say 20K miles. Didn’t cost that much either.
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@fletchG I am thinking that it could be I’m not quite shifting enough fluid to free the clutch completely - so I am probably going to install a master cylinder overhaul kit and see what that does.
@Phil here are the two types of slave with springs
Makes sense; I’m going back to my Ducati days here and I kind of forget what drove me to replace the original… but amazing how much lighter it was afterwards. In my more recent Guzzi days, my V50 has a somewhat less exotic actuator 
. Hope it all works out. G
Hi Brian, thanks for the photos. Which cylinder is which? Ie original and Oberon? The springs don’t look identical the silver coloured one looks longer and made from thicker wire. I don’t understand what looks like three pistons can you explain the assembly of each cylinder. From the photo it looks like the right hand cylinder has a much smaller bore than the other one. I’d you measure the bore of each you can calculate the difference in piston movement when operating the handle bar lever. An example being: if one cylinder has a bore diameter of 20mm and the other 15mm the difference in piston travel of the 15mm bore cylinder will be close to double that of the 20mm diameter cylinder. If the larger bore cylinder is the Oberon version it explains your problem of lack of clutch disengagement. However the handlebar lever force required to operate the clutch will be reduced because the piston is travelling less than the standard piston. If all the above is correct then your only option is change the handlebar lever piston diameter to move more fluid to compensate for the larger slave piston. This, of course, will increase the required lever force and you are back to square one. I think you should talk to Oberon and ask them how they expect their replacement cylinder to operate on the Moto Guzzi clutch set up. Do Oberon make a direct replacement of the Moto Guzzi slave cylinder? Ie one made to the same dimensions? It sounds like the Oberon cylinders are well made and offer smooth operation which could be an improvement but changing the cylinder bore is a problem. Going back to the start of this thread, “Speedy” asked if any one had fitted an Oberon to a Moto Guzzi and if so were there any issues. It would appear that a couple have had good experiences with Ducatis but no one has come forward with a comment re Moto Guzzi. I really think talking to Oberon is your best bet. Cheers Phil
This is the Oberon, on the previous picture the large piston is the “old” slave before being superceded by the small piston model.
The 2 large pistons are an original worn out one and a new stainless one.
Thanks for the explanation Brian. From what I now understand is that Moto Guzzi “upgraded” from the large bore cylinder to the small bore cylinder. Ie they increased the stroke of the piston . The Pberon piston is large bore, therefore of the short stroke type. You need to ask Oberon a small bore piston to replicate the Moto Guzzi upgrade. Of course the small bore slave cylinder will increase handle bar lever force required to operate the clutch. Cheers Phil
And do not forget that Oberon slave cylinders usually have a slightly wider bore than the OEM item to reduce lever effort, so this could well be the source of the problem.
Did Oberon change the bore of their slave to reflect the change in OEM spec?