If the clutch fluid is discolored, I'd change it regardless of the age.  Not sure why it would be so different from the brake fluid though.  Anyone have a theory?

Brake fluid is hydroscopic, meaning it absorbs water. As it does this, it changes color from clear to very dark. This is an indicator as to how much water the fluid has absorbed and a great 'yardstick' by which to gauge when to change the fluid; anything darker than, say, tan and the fluid should be changed.

That applies to brake systems but not necessarily the clutch because clutch fluid always gets darker, faster than brake fluid. The reason is that the hydraulic parts internal to the clutch move much more and so wear much more than brake parts. Some of the darkness of clutch fluid is actually metal fines worn off the master and slave cylinders. Brake systems are effectively zero movement systems in which the master cylinder is used only to pressurize the system, not really move anything. Of course the brake pads do move but it is only a few thousandths of an inch. The clutch on the other hand is always used for its full travel whenever it is used; both the master cylinder and slave cylinder move throughout their entire travel each time the clutch is used. Add to that that the clutch is used more often than the brakes and it ends up that there is a lot more piston travel, and resulting wear, in the clutch than either or both brake systems.

This was my clutch slave cylinder after something like 50K miles- the areas showing wear have had some steel removed in the form of fines (extremely small particles) and it ends up in the clutch fluid because it cannot go anywhere else.



Brian

I believe the manual says change the clutch and brake fluid every two years. I noticed on my morning ride, that the color of the brake fluid still looks clear while looking at it through the little site window. but the clutch fluid is very dark, almost black looking through the plastic window.
only had the bike for 10 month, almost 10k miles on it.
should the clutch fluid be changed more often or just go the two years?

I change the fluid on my bike whenever it gets to a tan or brown color. The stuff is pretty inexpensive and fairly easy to change as long as you do not suck any air into the system.

Brian

OK thats good enough for me. I'll change it out, I have a hand vac pump.

I think heat plays a bigger role in breaking down clutch faster than the front brakes.
The clutch line runs right next to the engine.

Most of us don't use the brakes as much as we think we do. Nor do we apply as much braking force as we think we do.
By the time someone gets to the skill level to buy a C-14, they pretty much know how to ride. It is the Number 1 old farts bike.


Ever owned a Ducati?
All of my rear brakes turn brown within a month with the Res. right next to the rear cylinder exhuast header pipe.
The clutch is brown within three months.

Brake fluid is hydroscopic, meaning it absorbs water. As it does this, it changes color from clear to very dark. This is an indicator as to how much water the fluid has absorbed and a great 'yardstick' by which to gauge when to change the fluid; anything darker than, say, tan and the fluid should be changed.

That applies to brake systems but not necessarily the clutch because clutch fluid always gets darker, faster than brake fluid. The reason is that the hydraulic parts internal to the clutch move much more and so wear much more than brake parts. Some of the darkness of clutch fluid is actually metal fines worn off the master and slave cylinders. Brake systems are effectively zero movement systems in which the master cylinder is used only to pressurize the system, not really move anything. Of course the brake pads do move but it is only a few thousandths of an inch. The clutch on the other hand is always used for its full travel whenever it is used; both the master cylinder and slave cylinder move throughout their entire travel each time the clutch is used. Add to that that the clutch is used more often than the brakes and it ends up that there is a lot more piston travel, and resulting wear, in the clutch than either or both brake systems.

This was my clutch slave cylinder after something like 50K miles- the areas showing wear have had some steel removed in the form of fines (extremely small particles) and it ends up in the clutch fluid because it cannot go anywhere else.



Brian

Excellent post Brian.  Makes all sort of sense.  Thank you.

There is a large black plastic floating piece in the clutch reservoir, iirc, and that may be what you are seeing as black.  That being said, change the fluid at least every other year, if not yearly.  Protect your painted parts.  Don't overfill the brake reservoirs if you are close to pad replacement time or you'll overflow when you push the pistons back.  Also, take note of the cover gasket for the reservoirs.  It kind of hooks around the top edge of the reservoir.  If you don't get it fully on it may start to leak and spray brake/clutch fluid all over your jacket and the top of your bike.  damhik.   

Thanks for the tip.

Start with clutch fluid change. You may be surprised how bad the brake fluid maybe after you see fresh stuff. Also, how does the back brake fluid look like? Dont forget about that one. You can buy the smaller brake fluid container and do front rear brake with clutch.

This bike also has bleeders at both brake and clutch master cylinders.  My other bikes do not have this feature.  Is it necessary to bleed through those first when changing the brake fluid?  the only reason I see is to replace the old brake fluid from the master cylinders first without pushing it through the whole system.

If I'm flushing the system just to change fluid, I don't touch them.  However, when I put on my Heli ST bars and had to add extension lines to each system, those bleeders came in mighty handy.  Darn good idea from Kwak to add them.

Thanks Jim, now I have to find time to change my brake and clutch fluids.   Without even looking a the bike, what plastics, if any I need to remove to access the rear brake master cylinder reservoir?  On one of my other bikes, it takes a lot of work to get to it. 

The rear master is under the seat from what I recall.  No need to take any plastics off.  Which reminds me, I need to flush the rear brake and I need to go by the Kwak dealer and get some brake fluid.  I've used all mine up with the ST installation.

correct, rear brake master cylinder reservoir is under the seat.