Hi folks, anybody knows what's the piston diameter in clutch master cylinder (2005 s2r800)? Bike's currently in the garage being serviced and not gonna have it back for at least a week. While they're replacing valve shims and doing tb sync, I want to prepare myself for rebuilding clutch master cylinder, and not sure what size kit do I need. Any help?

My clutch drags more than it should do. Bike creeps forward quite a bit, neutral is nearly impossible to find. So far I've done the following:
- replaced the whole clutch (inner/outer basket with the gear, hub, springs, throwout bearing) with brand new parts
- checked plates - all within specs
- replaced slave cylinder for OEM one, also tried aftermarked but it did drag due to different size bore
- checked pushrod, it's perfectly straight, replaced orings, greased with moly
- bled system million times, garage did it for me once professionally and still the same
- tried longer/shorter clutch springs (the 6 big ones) both within specs, also tried shimming them - none of it made noticeable difference

Everything was torqued to specs and checked with service manual step by step.

I'm thinking if it's not the mc or plates (this is next and last thing I'm gonna replace if it's not mc, other than engine oil), there's a problem with gearbox.

What grade engine oil?
Clutch lever adjustment screw?

It's running on Motul 5000 10w40 (semi synthetic) which I've put in 2950 miles ago.
The adjustement screw is in quite a bit. In fact it's almost all they way in if I remember correctly. There's about 2-3mm of freeplay before it pushes the piston.

Do check the free play at the clutch lever.  People sometimes use it as a service adjustment.  It is not.  You want 1.5-2mm free play.  Too much and you will not disengage fully.  Too little and it will slip.  The clutch bore will be a cast number on the cylinder.  PS followed by a number.  I doubt you will find a rebuild kit for that master.

There is also a possibility that you still have trapped air even after several bleedings.  Most surefire method?  https://www.youtube.com/watch?v=6OnQmWnDFvA

Some drag on your bike is normal on a cold start.  After a few blocks all should be fine.

If memory serves, you have a clutch basket from a different model installed. Do the two different models use the same pushrod?

Quote from: howie on January 03, 2020, 05:37:28 AM
Do check the free play at the clutch lever.  People sometimes use it as a service adjustment.  It is not.  You want 1.5-2mm free play.  Too much and you will not disengage fully.  Too little and it will slip.  The clutch bore will be a cast number on the cylinder.  PS followed by a number.  I doubt you will find a rebuild kit for that master.

There is also a possibility that you still have trapped air even after several bleedings.  Most surefire method? https://www.youtube.com/watch?v=6OnQmWnDFvA

Some drag on your bike is normal on a cold start.  After a few blocks all should be fine.

Like I said the adjuster screw is in quite a lot but there's a 2ish mm freeplay - I remember setting it to what service manual says, but can't remember exact figure now.

I'll check the number when I get the bike back, thanks; was hoping someone knows so I can order one now! Hopefully I'll find one

I'm sure it's bled properly. I know people often say it and they're wrong, who knows maybe I'm wrong too, but I bled it myself many times with speed bleeder at slave and mc (I installed bleed nipple there). Decent garage also bled it for me afterwards using big ass vacuum pump (it was still dragging so I thought I messed up), but they didn't see any air bubbles and it was still the same. I don't think there's any air trapped in the system.

About the drag, yes it gets better when it's warm but it's still not what I expect. It still creeps forward quite a lot, and it's easy to stall a bike (it's idling at 1000 so that doesn't help).

Quote from: ducpainter on January 03, 2020, 05:51:55 AM
If memory serves, you have a clutch basket from a different model installed. Do the two different models use the same pushrod?

That's correct, it's off 620 but the part number for the "clutch control rod" is the same - 11721192A

Just a thought.

Quote from: ducpainter on January 03, 2020, 06:31:37 AM
Just a thought.

It's a very good thought, to be honest with you I didn't check it when I replaced the basket - so thanks for pointing it out

Was the slave you installed new? There's a spring inside the slave that keeps the piston in contact with the push rod. If there's corrosion on the outer part of the slave bore, the spring might not keep the piston in contact, so you'd lose travel due to the piston having to move before it can move the push rod.

Quote from: ducpainter on January 03, 2020, 09:38:40 AM
Was the slave you installed new? There's a spring inside the slave that keeps the piston in contact with the push rod. If there's corrosion on the outer part of the slave bore, the spring might not keep the piston in contact, so you'd lose travel due to the piston having to move before it can move the push rod.

The OEM slave was ~5k miles old when I bought it (8k now) and in very good visual condition. Is there a way to take it apart without damaging anything and inspect inside? I still have my old one (known to leak) so I guess I can try on that one first.

I have an idea I was thinking to bleed the clutch again before touching master or slave. If there are no air bubbles, and it's still the same, that eliminates bad master or slave and narrows it down to the clutch pack or/and other components - am I right? If one or the other leaks, I'd either see fluid on reservoir or slave's piston, or air in the system, right? In this case I think I'd just buy new clutch pack and oil, and hope it fixes the problem

You could remove the dust seal, push the piston all the way in and get an idea about the condition of the bore.

The problem with your bleeding theory is just because you don't see any air, doesn't mean it isn't there. Ducati clutches can be problematic, especially when you replace a component and the system gets drained.

Worn clutch plates never drag, only slip. It could be an oil issue, but again, the wrong oil usually causes slipping, not drag. Do both bikes use the same clutch pack?

and stack height?

Quote from: ducpainter on January 06, 2020, 03:36:06 AM
You could remove the dust seal, push the piston all the way in and get an idea about the condition of the bore.

Thank you, I'll try it on my knackered slave first to see if I break it lol. Last thing I want is to buy another slave again or rebuild kit

Quote from: ducpainter on January 06, 2020, 03:36:06 AM
The problem with your bleeding theory is just because you don't see any air, doesn't mean it isn't there. Ducati clutches can be problematic, especially when you replace a component and the system gets drained.

If I see no air bubbles and it doesn't feel spongy, I can only assume there's no air so yes you're right, but I can't think of any way to make sure it's 100% air free?

Quote from: ducpainter on January 06, 2020, 03:36:06 AM
Do both bikes use the same clutch pack?

Both bikes use the same clutch disc set part no 19020161A. Thing is, I have 2 clutch packs now (s2r and 620) but one of them must have aftermarket friction plates - they look different.

Quote from: ducpainter on January 06, 2020, 03:36:06 AM
Worn clutch plates never drag, only slip.

AFAIK clutch can drag if steels are warped! I can't be 100% sure if mine are warped as I don't have perfectly flat surface at home to check. Basically I mixed steels from 2 sets and picked the 'best' ones.

Quote from: ducpainter on January 06, 2020, 03:36:06 AM
It could be an oil issue, but again, the wrong oil usually causes slipping, not drag.

It could be as simple as that, I doubt it's the oil though. Anyway, sometime soon I'll be changing it, so I'll try silkolene instead of motul to see if it makes any difference.

Quote from: howie on January 06, 2020, 03:55:14 AM
and stack height?

IIRC stack height is 52.5mm - manual says it should not be less than 50mm. If I remove thinnest steel and friction, it will be less than 50mm.

You're right. Warped steels could cause it because the stack is, in effect, too tall. Buy a piece of window glass, or use a mirror. That would be flat enough.

Sometimes, depending on how the stack is built, you can just remove a steel. IIRC steel plates come in 1.5 and 2 mm thicknesses. Friction on friction does no harm.

Also, if you have 2 packs, you can look for the thinner steels and replace one of your thicker plates to get the stack around 52 mm. It shouldn't take much to cure this issue. What color are the friction plates? You may have chosen the A/M plates which is causing your issue.

Quote from: ducpainter on January 06, 2020, 05:50:05 AM
You're right. Warped steels could cause it because the stack is, in effect, too tall. Buy a piece of window glass, or use a mirror. That would be flat enough.

Sometimes, depending on how the stack is built, you can just remove a steel. IIRC steel plates come in 1.5 and 2 mm thicknesses. Friction on friction does no harm.

Also, if you have 2 packs, you can look for the thinner steels and replace one of your thicker plates to get the stack around 52 mm. It shouldn't take much to cure this issue. What color are the friction plates? You may have chosen the A/M plates which is causing your issue.

I think just the friction plates are aftermarket, steels look the same. I don't think I have any thinner steels in my packs to get the stack height any lower, I've put aside ones I think could be warped and I'm left with just the right number of them. I will however check again and use a mirror! It's a good idea to remove one steel plate if friction to friction doesn't cause any harm - I wasn't too sure about it, thanks!

Also I just figured I can measure the stack height at various points. I guess if there's any difference, that means some steels are warped.

Another thing - the 6 clutch springs. Again I have 2 sets of them, the measurement differs between 2 sets but both are within specs. I cannot find new OEM ones anywhere unfortunately. I'm a little confused about them - which ones the longer or the shorter springs would help the clutch disengage easier? I know it also depends on their springiness so it's not the best comparasion, but would you suggest using shorter or longer ones in my case, if both are within specs? The way I think is, longer (assuming stronger) springs are compressed when the clutch is engaged, and they decompress when clutch disengages. Therefore, if it's not slipping, longer springs should theoretically help to disengage clutch better?

I know it's a long shot, but does anybody know what's the stack height on a factory new bike?