fastD

About a year ago I had the clutch MC fluid replaced, The fluid remained clear until two weeks ago when it turned dark, I had the fluid change yesterday and now a day later It's turning dark again, I'm concerned a problem may be developing. Any ideas?

windhund116

I'd try re-siphoning the brake fluid and adding new stuff back. May need to do this a couple times. If still getting dark, too soon... could be master cylinder seals going bad.

Good luck!

Mr.Matchbox

On every Motorcycle with hydraulic clutch, the brake fluid will turn dark-black within weeks after the change. The same happend also on my CRX del Sol.
I dont know why....Maybe the rubber seals for the clutch are different from the ones for the brakes.
The clutch mechanism works fine and reliable nevertheless, so i dont care anymore. Just change the clutch fluid together with the brake fluid every two years and you are fine.

Car Analogy

Most motorcycles use a wet clutch (clutch disks immersed in engine oil). Most cars, and the S, use a dry clutch.

The reason the S clutch fluid gets dirty is because the slave resides in a very dusty environment. Each time shaft is extended, it picks up tracesof this dust, which are able to work past the seals. Fluid gets contaminated.

Dirty fluid will eventually cause the fluid to leak from MC and slave cyl seals (MC will leak onto carpet).

But since clutch fluid is circulated during pedal application, if you regularly just swap the fluid in tbe reservoir, the fluid will be constantly renewed and kept at a state of clean enough. Do a resevoir fluid swap at every other oil change (or if you go longer intervals, for example following maintenance minder, every oil change).

If your fluid hasn't been kept up in this way, initially do a full fluid swap via gravity bleed, being careful not to let reservoir go dry during process. From there just do reservoir fluid swap.

I use a fluid syringe I got from Harbor Freight. A turkey baster bulb type works also. Just be careful about spillage. Towel over the fender, another under reservoir.

fastD

The fluid was clear for about 10 months then it changed. The new fluid was only clear for less than 8 hours. Thinking seals are the issue.

GuthNW

On every motorcycle with a hydraulic clutch? I've only owned one motorcycle with a hydraulic clutch, but with just the one this has not been my experience.

I know that dry clutches place less drag on an engine but in the case of certain Ducati's running an open clutch cover for example I really don't care for the sound. But as far as the the wet clutch vs dry clutch on a motorcycle goes, for those motorcycles with hydraulic clutch activation I'm not sure how either would impact the fluid in the hydraulic system one way or the other. Can you explain further or is that not the point you are making?

Car Analogy

The point I was making is a wet clutch won't allow clutch dust into the hydraulics, since any dust will be immersed in oil, and the hydraulics are external to crankcase.

So if anything, a typical wet clutxh motorcycle cannot dirty its clutch fluid in the same manner the S clutch fluid does.

Mr.Matchbox

@ GuthNW. Yes, on every motorcycle with hydraulic clutch.

@ Car Analogy: Not on all, but on most Motorcycles, the clutch slave cylinder is mounted outside of the crankcase (e.g. on the chain sprocket cover) , the clutch is actually pressed with a little push-rod that has is own shaft seal in the crankcase.

Car Analogy

Right, that's what I said. Hydraulics are all external to crankcase.

GuthNW

I still don't understand why Mr. Matchbox's experience with the brake fluid in the clutch's hydraulic system turning dark so very quickly occurs. Are you riding street or dirt?