I am edging closer to getting the '91 SS back on the road. I probably should have created a single thread rather than ad-hoc posts for every issue. Anyway, one of the final jobs is to bleed the clutch. I fitted a brand new Oberon slave as the original one had vanished. I refilled the master cylinder "coffin" with fluid, and attached an "easy bleed" hose and bottle (filled with the appropriate amount of fluid) to the bleed nipple at the slave end. Following the standard bleeding procedure, nothing seems to be happening at all. Even with the bleed nipple completely removed, pumping the clutch lever doesn't appear to produce any fluid at the slave end, just very tiny drops sporadically. I then removed the hydraulic cable at the coffin end, and placed a rag underneath the opening. Even then, pumping the lever only produced a minimal amount of fluid - I was expecting to see it gushing out. I then extracted all the fluid from the coffin so I could try and see what's going on behind the two tiny holes in the base of the coffin, when the lever is pulled. I can see movement - presumably the piston inside? So I am thinking either the master cylinder is a goner, or I'm doing something seriously wrong. Could it be blocked/partially blocked on the inside, somehow? If the master cylinder is at fault, can it be fixed or is it throw away and buy a new one? Not quite sure what to do next.
If the master is full of fluid, it should produce bubbles from one of the holes when it is pumped, as the air in the line is replaced by fluid. I would close the bleed at the oberon initially to see if that helps get a bit of fluid going down the line. If it doesn't produce bubbles at all, your seals may need replacing, and I would imagine it's a PS13 master and you can get the parts for this still. You are seeing the piston through those holes. That's where the bubbles of air should come out. I suspect, if its an old master, that it needs a service kit. Not hard to replace and gives piece of mind, but try the above first.
DQ’s advice is sound. Long shot but I also think it’s possible to inadvertently stop the piston returning far enough to accept or release fluid from the (larger) feed hole if you have an aftermarket lever, or, the grub-screw adjuster on a standard lever is protruding a long way, enough that the piston is not free to come to it’s real end point. I would make sure that when the lever is out, there is a small air gap between the adjuster and the piston.
@KevB did you manage to get yours sorted? I've just tried again this morning, closed up at the slave end, but still not happening. I am not really seeing any bubbles at all, although when the coffin was drained, I could definitely see the piston action. Then, having also read Kev's post, tried the suggestion of removing the output line at the coffin end, and bunging up with a finger while operating the lever. Again, minimal bubbleage. So I draw the conclusion that the whole shebang needs to be removed and serviced. Thanks for that info @Desmoquattro - service kit is available for about £30 Which begs the next question - how to remove the lever and master, as it appears that the handlebar bracket is conjoined with the choke assembly! Can they be prised apart? The bar itself could also do with a lick of paint/pc, as you can see.
Not yet. Trying again later. The MC has had a full service new seals, new piston, etc. so this is just user incompetence it would seem...
@ck_uk remove l/h switch assy to reveal small screws for fixing the choke lever, did you prime the oberon slave before attempting to bleed from m/c?
Let us know how you get on, sometimes it just takes ages to bleed, but a new kit will no doubt solve your problem
The efforts continued. I primed the slave, which already seemed to be full of fluid anyway, but this didn't make any difference. Finally, in conclusion that the MC will need a service kit, I began the process of attempting to remove the lever and master assembly from the bars. Got the switchgear off and pulled the grip, which needs replacing anyway. I was then able to see the screws attaching the choke housing to the master. I was only able to unscrew one of these; the other just seems impossible to get at regardless of how far round the choke adjuster is moved. It seems like the adjuster part should possibly detach upon full rotation; maybe that is the key. But whatever I try, I can't access the other screw to remove the unit. Threw the towel in on that and turned my attention to bleeding the rear brake. Oh no you don't. The bleed nipple is 11mm but the open end of my 11mm spanner won't fit, and although the ring end would (having checked on a front brake nipple), the proximity of the hydraulic line doesn't allow space for a ring spanner. It doesn't seem like a brilliant design. Perhaps I have a bad spanner. Or perhaps I am just being thick.
Most 11mm sockets with 1/4 drive are thin wall enough to fit and are a safer bet than an open ender regards rounding. But if you only have that combi 11mm and the open ender won’t fit maybe a brass wire brush of the nipple will help.
If you’re going to bleed the system, why not undo the banjo, thus gaining full access to the bleed nipple? Tightening it up once bleeding is finished should be manageable with an open ended spanner
Thinking back for access to screws the choke lever rotates and comes off, but possibly you might have to remove the clutch lever to get it to rotate enough. Cheers Gaz
Be carefull with the screws, they are small and I had one snap off. I did end up buying a new master cyl as the bore had a bit of corrosion when I stripped it and would not clean up. If it's not looking like they are coming out try ususl wd40 and or a bit of heat. I did successfully drill out and added a thread insert if it does snap. There is a technique to getting the piston out, which I found after I had butchered it. I believe you take the banjo out an insert a rod down the hole and knock the piston out. It is held in by a pressed in ring, unlike the brake which has a circlip. I will post pictures later and see if I can't find the stripping proceedure. This may be usefull, but I am sure I read you could knock it out as I described. http://forums.ducatipaso.org/viewtopic.php?t=8289 Cheers Gaz
A replacement master cylinder is an option if they are still available, which I think coffin reservoir PS13's are, but if not (for example Brembo round reservoir PS12) and you want to maintain originality, it's possible to get them sleeved if it's only the bore that is corroded/pitted from standing in a barn or similar. The cylinder is bored out and a stainless sleeve pressed in and bonded in position, the two small holes to the reservoir are drilled and then the sleeve reamed to size, and you can then fit the new piston, seals, spring, etc that come with the kit. One of the companies that do this is Past Parts in Bury St Edmunds, around £50 plus VAT + shipping, and obviously + cost of repair kit. I didn't know this was a 'thing' until I did some research, apparently quite a common thing on classic cars where OEM parts are no longer available. As the sleeve is stainless then it's not going to corrode if left standing with water in the brake fluid. HTH.
Brembo Clutch Master Cylinder 10467014 for Ducati SuperSport 900 91-97 (carpimoto.com) Edit: not had an issue buying from Carpimoto, but if you prefer to buy UK try this chap.(£135) Master Cylinders (ducatipaddy.com)
I looked at some parts from Caprimoto and at the time would not ship to UK, either up to or over a certain amount, not sure if this is still the case. Just found this. ck_uk, I will see if I can find where I got it, it was slightly cheaper than others I had seen. Just found it I paid £107 at the time but looks like they have gone up - alot soz. Cheers Gaz.
