Continuing - So what did you do to your bike today...?

[KiwiCol]

Here's another thought, wild I admit, But, I've heard you can send your used engine oil off & be tested for all sorts of things, maybe the clutch fluid can be tested to see what the contaminant is? 
It's probably in the skip by now though.

[T 24]

I have braided lines, clutch & brake, and those XJR & Bandit have their original ones.

[gsxbarmy]

I've wondered this myself before T24 and having researched it a bit, whilst I have no definitive answer, these were some of the reasons:
- clutch fluid works harder than brake fluid, in particular around the slave cylinder
- clutch fluid reacts over time to being in the proximity of a hot engine
- Water absorbed by the brake fluid gets warm (due to the engine heat) making the fluid deteriorate quicker
- clutch fluid reacts with the aluminium of the master / slave cylinder
- the rubber grommets in the master cylinder are the cause
- all of the above!

Anything definitive? Nope!!

[KiwiCol]

A couple of replies to the same question on the Ducati forum


Unlike the brake system, as the disc in the clutch wear, (and along with the natural flow of fluid in the system) fluid is displaced into the reservoir.  In a brake system, as brake pads wear and the piston is displaced further into the caliper, the fluid in the reservior decreases.  With the clutch, the fluid in the reservior increases, bringing along with it, any contaminants, crud, or dust that happens to get into the system.  If you'll notice, this is why you have a 'min' and a 'max' line on the clutch reservoir, but only a 'min' line on the brake.

We could argue how that gets into the system yes, but this is the reason it gets into the reservoir.  If look closely however (at least best I have noticed on all three of my Ducs) the crud ends up in the reservoir stuck to the sides or resting in the bottom and not suspended in the fluid.  I have never seen any detrimental effects from this, but I personally have never owned a Ducati that didn't do it.


and:


The crud is as previously stated aluminum and rubber. The fluid darkens as it ages because it is hydroscopic and the water it picks up contributes to the corrosion of the cyl. bore.The reason it turns color so quickly is the relative distance the seals travel is about 4 times greater than in a brake cylinder.And the loading on the seal increases as it slides down the bore unlike the brake which stops moving pretty much at peak pressure.Just change the fluid once or twice a year if it gets too dirty.




Which sounds logical & reasonable to me anyways.

[Blubber]

Does anybody know what is that black shit and from where it comes? Why not in brake fluids?
The fluid itself is the same DOT 4+ in all of those three bikes now, I cant know what fluid they had, but they were black.

Now that you mentioned it...
I once read it is dissolved chain spray.
Never given that explanation much thought.

[KiwiCol]

So, given my above post is correct, we'd have all the crud coming into the clutch master cyl & all the crud in the brake system going into the calipers.


Now, lots of you have stripped & cleaned your calipers, (I've not yet) so, how were they inside?   Black crud?

[Andre]

No black crud in the calipers.

Clutch fluid is worked more often and moved more distance. The exposure to heat and the grease/dirt mix do their part as well. It is conceivable to me that dirt gets in as there is no dust seal and the piston travels a good deal. Most of the piston is exposed to the outside (reverse is true for the brake piston) and in absence of a dust seal carries it into the slave cylinder. Dirt gets dispersed within the fluid and there is an inherent flow of the fluid in the system that eventually brings the crud into the reservoir.

Here some pics from my first clutch fluid change including slave cylinder/piston. No idea how long it had been since changed last. Doubt it was ever cleaned.

[grog]

Andre, reckon youve nailed it. works its way back up from slave. think i can remember, from old org, an extra seal that can be fitted to slave. maybe a busa thing, cant remember. Barmy knows, im sure he had posts on it. every year or so i clean pushrod, mix up the grease oil mixture recod in manual, just to keep that seal into motor happy. a rebuild needed if it stuffs up. internal fit only. takes not much time to do

[Andre]

Did that oil/grease mix treatment ad will do it regularly. Anything to avoid having to open up the engine. Gotto go now, the Lady wants me to rub her chain with some gear oil 

[Hooli]

I changed the clutch fluids. Fluids were totally black, and it was third time in five years I changed them. Brake fluids were changed also last time and they are still OK clear.
Same thing, black sludge in clutch fluid, in XJR 1300 and Bandit 1200..
Does anybody know what is that black shit and from where it comes? Why not in brake fluids?
The fluid itself is the same DOT 4+ in all of those three bikes now, I cant know what fluid they had, but they were black.

It's the heat of the engine. The fluid in the clutch is kept a lot hotter than the brakes so degrades quicker.

If you leave it in the brakes long enough you'd notice the front goes dark before the rear for the same reason.

[T 24]

If it is the heat of the engine, why the clutch fluid (DOT 4+) in my car keeps clear 15 years? And my car engine is running hotter than my 14.

[Hooli]

More airflow around the slave in the car? I dunno but it's made sense to me so I change the clutch fluid annually.

[gsxbarmy]

Fitted the Givi S250 Toolbox to my Triumph. Lockable and waterproof, impressive bit of kit

[IanH]

Fitted my PUIG screen today and took it for a little test. Looks pretty okay and although the difference is not huge it is noticeable.
At £35 delivered can't really complain.

[Notty]

Polished my engine cases today - is there anything that can be put on to protect them from becoming dull again?