Experience with master cylinder rebuild?

[d3vi@nt]

Just to update... I got a set of RCS levers; 16 for the clutch and 19 for the front brake.  Sweet hardware, but ran into some fitment issues. These MCs are straight, so don't have the same angle as OE. While the brake has mounts for microswitch, the clutch lever does not. Meaning I would need a banjo bolt with a pressure switch, or deal with no microswitch, which I'm disinclined to do. Also, the OE's have a bolt hole in the top for securing hand-guards. The RC's lack this, so hand-guards can't be secured there.

Still trying to decide if the combined minor issues = deal breaker.

Since I had the clutch MC off, I decided to take it apart to see what I could see. It's literally a pin, spring, piston, and a snap ring to keep it all in place, covered with a dust seal. Can Brembo really not make a rebuild kit available!?

Regardless, the piston seemed pretty dirty (as in black particles). The dust seal had a few small tears, so it could be ingress but wondering if it's seal breakdown.

Is there a recommended cleaner for piston and seals that won't cause the seals to degrade? Rubbing alcohol?

[Speeddog]

I'm pretty sure a banjo bolt pressure switch would trigger at too high a pressure to work for the clutch.
No they're fine.

The seal on the piston is the one that really matters.

WD40 is a good cleaner that won't hurt things.

[d3vi@nt]

I'm pretty sure a banjo bolt pressure switch would trigger at too high a pressure to work for the clutch.

The seal on the piston is the one that really matters.

WD40 is a good cleaner that won't hurt things.

Thanks for that info.

Speculation as to where the grunge might come from. Some feel the line from MC to reservoir is suspect.  I ordered up some clear Tygon 2375 to see if that helps at all. Potentially seal degradation, but I can't tell on inspection. Could still be ingress from small tears in the dust cap.

I also learned that there was a recent recall for the 16 brake cylinder for various models. Because of that, the piston kit is available (part #61041881A). I've ordered one to see if it is identical to the clutch and possibly use that, or just the seals if they're identical. Could be that a thorough cleaning of the existing cylinder and seals will do the trick. Hard to say since I have no idea what the source of the leak is.

[Speeddog]

I'm pretty sure that the contamination in the fluid on the clutch systems is metal from the master and slave cylinder pistons and bores.
IME, it's particulate, if you let it sit for a while it will settle to the bottom of the reservoir.
I don't think it's the black OEM reservoir hose material.
Systems with clear hose or no hose still get black.

Brake masters and calipers move very little in comparison, and my SWAG is that the clutch is actuated 5x as often.

Also, the clutch slave cylinder spends a lot of time quite hot, that doesn't help the fluid at all.

[d3vi@nt]

I'm pretty sure that the contamination in the fluid on the clutch systems is metal from the master and slave cylinder pistons and bores.
IME, it's particulate, if you let it sit for a while it will settle to the bottom of the reservoir.
I don't think it's the black OEM reservoir hose material.
Systems with clear hose or no hose still get black.

Brake masters and calipers move very little in comparison, and my SWAG is that the clutch is actuated 5x as often.

Also, the clutch slave cylinder spends a lot of time quite hot, that doesn't help the fluid at all.

I'm pretty curious. Looking at the design with it disassembled it seems the only thing that comes into contact between the piston and the cylinder are the seals. It doesn't seem that the seals are stout enough to remove metal from the cylinder?

The piston seems metallic, though not magnetic, so not sure what it's made of. The recalled pistons affected various '15-'18 models and were made of polyphenilene sulphide (PPS). The replacement units are machined from aluminum bar. For whatever that's worth...

When I got the bike, I could see particulate on the bottom of the reservoir. Not a huge amount but enough to notice. I cleaned it out completely. I haven't seen it return, but I've been flushing/bleeding a lot with the leak plus the Oberon slave replacement. When I disassembled the MC, the piston wasn't visibly dirty, but the rag I wiped it with showed quite a bit of the same black particulate. No clue if it's significant enough to compromise operation. Seals appear to be fine to my untrained eye.

Waiting on the repair kit at this point. Funny thing is, Ducati wants $27 for just the MC dust cap. The kit that costs $20 includes it. And I read that the exact same dust cap can be purchased from the KTM dealer for $5. 

[Howie]

I believe the black is from heat.

[Speeddog]

Anybody got access to a mass-spectrometer or some similar apparatus?

What about those oil analysis people?
What do they use?

[Howie]

Anybody got access to a mass-spectrometer or some similar apparatus?

What about those oil analysis people?
What do they use?

I suppose you could call one of the oil analyses companies and ask about testing brake fluid for contamination other than water.  Or maybe a small local chem lab.  Something definitive would be nice.  This black brake fluid discussion a has been going on forever.  What makes me think heat is the water cooled Multistradas.  If the cat is in place, black rear brake fluid.

[Speeddog]

I suppose you could call one of the oil analyses companies and ask about testing brake fluid for contamination other than water.  Or maybe a small local chem lab.  Something definitive would be nice.  This black brake fluid discussion a has been going on forever.  What makes me think heat is the water cooled Multistradas.  If the cat is in place, black rear brake fluid.

That's some good info right there.

Haven't seen but a few MTS1200 myself.

[d3vi@nt]

Good ideas. I never thought about fluid analysis. I'll see who or what I can dig up.

Something definitive would be nice.  This black brake fluid discussion a has been going on forever.  What makes me think heat is the water cooled Multistradas.  If the cat is in place, black rear brake fluid.

Agreed. The MTS rear brake has been another source of speculation. A number of folks on the MTS forum have still encountered the issue with cat removed. As a result, the ABS unit has been suspect. Though the front brake fluid is not prone to the same degradation as the rear, though it obviously goes through the same ABS unit. Folks seem to have good luck with the spendy Castrol SRF and its higher boiling point, though.

My issue right now though is clutch going bad after 250-300 miles, fixed by bleeding the MC each time. Slave was removed from the equation with new Oberon unit. OE rubber clutch line could be a source, or leak somewhere involving the MC.

I've never had a clutch MC apart to know if the black residue on the piston/seals is normal or excessive. Since the seals appear to be okay, I started to wonder if the residue was sufficient to allow air into the system. Visual inspection overall hasn't yielded anything, so I'm left to guess and replace what I can.

Will keep updating. Thanks again for the insights and discussion 

[Speeddog]

I'm pretty sure a banjo bolt pressure switch would trigger at too high a pressure to work for the clutch.
~~~SNIP~~

Not sure where I pulled that idea from. 

Just tested one mounted on a clutch and it switches at low effort.
Should be fine.

[koko64]

A mate has the RCS masters on his Superlight and they work great. The adjustable pivot ratio feature lets you fine tune them for feel. It meant buying the bracket kit for the resi's or making some. Thinking about it, I don't know if I'd want the m/c supporting a bark buster anyway.

[d3vi@nt]

I ended up returning the RCS levers. Nice hardware, as I said, but fitment issues were bothersome enough.

Repair kit arrived yesterday and the piston is identical. Funny part is that the $20 kit contains the $25 dust seal

Info about the recall, parts involved, and rebuild instructions here, in case anyone needs it or is interested: https://static.nhtsa.gov/odi/rcl/2017/RCSB-17V812-2711.pdf

I hope to get everything back together this weekend. Temps dropped drastically coupled with early snow, so I'm not sure if I'll be able to get the miles in to fully test. We'll see.

[d3vi@nt]

Well... I wasn't as clever as I thought I was. While it appeared identical, the piston was just hair too large and would not fit.

So, I gave everything a good cleaning, reassembled and bled with fresh fluid. I'm hoping that will return function to normal. I was able to use the new dust cap, at least. 

[Howie]

Ah, the recall.  What is the piston made of?  If it is plastic Ducati has to fix it for free regardless of...well...anything.