I have just measured both and I can confirm 26mm bore for the cover/sleeve and 25.95 (or thereabouts) for the piston.
the bore is definitively 26mm

My new cover (the OEM racinc version pre drilled) at the very bottom of the bore has a channel that goes all around connecting the two holes for the bleeder and the pump; the width is around 3-4mm and is aprox 0.5-1mm deep.

basically when you sleeve the cover there is no need of going to the bottom anyways as I think the piston does not get bown there and if it does it is only for few mm.

I think we are overthinking the whole issue, stick a sleve in, making sure the botton /holes are free, bore it to 26mm and assemble

thank you!

Very curious if you sleeved the clutch slave bore.
Any pictures?
If mine would start leaking I certainly would consider this solution, so I'm very interested to know if it works ......
Seems like a straight forward job.

Frank

A very late reply, but I've had 2 bearings go in the slave piston on my 750, the second in particular appears to have spun the piston and grooved the bore. I put a new piston in as an experiment but the clutch action was far from smooth, I assume as the piston was tilting and catching on the grooves. I asked Paul K at Ducati Technical Services at Wakefield, UK, about it, as I feared new covers are unobtainable but he agreed to resleeve the bore, this was quickly done and the clutch action has been smooth and predictable since. I would imagine the bore surface could be better than original. I've only done about 1000 miles since but all seems OK so far.

Martin

Martin, do you have a picture of the resleeved clutch cover? What did it cost? Would like to have one of mine resleeved also ....

Frank

So I can report that while the sleeve job appears to have been done well, it seems that during the process, it created a crack (or two) in the fluid channels of the cover. I had a steel sleeve inserted, and they were able to remove bore material right down to the fluid channel that exists at the bottom of the bore (you can feel it if you run your finger around the bottom of the bore). They did a fantastic job with the over-bore and sleeve. However, upon reinstalling it, I was never able to build up pressure in the lever, and somehow the cover was weeping fluid.

Since I couldn't see the source while it was on the bike, I pulled the cover, line & master and made a jig on my bench so I could bleed it up there, clamping the piston into place to simulate it being on the bike. I dried the inside of the cover and lo & behold, once I got the air out, any pressure in the system would cause a weep through a crack, possibly two. It appears to be in between the fluid inlet channel (from the hose) and the air bleed channel; possibly another towards the bottom - neither of which are easily visible.

Since this wasn't happening prior to the 'surgery', I have to assume it was some artifact of the sleeving process. I was considering trying to thoroughly scrub the interior of the cover and use some JB Weld for aluminum to see if I could patch it, but I don't know how well that would stand up to the heat+vibration+continuous fluid pressure changes. I just get the feeling I'd wind up on the side of the road without a clutch at some point. So I've sourced another used cover, and I'm going to go with that.

I feel like I'm exchanging the devil I know for the devil I don't, but hopefully it'll mean the bike will be reliably back on the road in short order. Worst case, this new-to-me cover needs a sleeve; and quite possibly I'd give that a second shot. My shop only charged me $100 to do the sleeve. (The crack may have just been an unfortunate occurrence; I've got ~30k miles on my Paso, and it's had a workout for most of that.) Not that I'm thrilled about the cracked fluid channels, but as it's been nearly a year since I had the work done, I'm just going to let it go. I had so much trouble with the clutch over the past year, and the year prior, I wound up just letting it collect dust until this year. (Which only gave the mice ample time to make a formidable nest behind the seat, just above the rear light ... so the bike also got some wiring upgrades this summer, too).

But, here's pictures of the new steel sleeve ... prior to having clutch fluid leak all over it.

With any luck, the new cover will solve all of this ... so much for 'fixing' it.

What a shame. The sleeved cover looks so good too.

Hi Jake,

JB weld (epoxy glue) is a perfect solution for small cracks!
Have used it also in the past, will perfectly survive the environment of the clutch.

Alternatively, you could use Lumiweld which is also perfectly suited for this application.

Any, idea whether the sleeve uses a shrink fit or if it is glued in place?

Good luck!

Frank