First off. I apologize if this gets a little long winded...and for putting it in the touring section vs. say under a more topic correct section. I just thought it might be of interest to other people and it has a better chance of being read in here.

So what this is all about is an answer to why my hydraulic clutch fluid keeps turning to a graphite gray looking color. After talking with techs at two different dealerships. I was no closer to the answer. I was also no closer to understanding why after bleeding the clutch line I would have clutch engagement much sooner when I let out the lever. What I mean is the clutch would start to grab when the lever was only 1/2-3/4 of an inch off the handle bar. And I liked it that way. But it would quickly get much farther out after a few short rides. The master cylinder was replaced under warranty just a few weeks ago hoping that this would solve both problems (to me anyway).

It did not so I kept looking for a solution. Now on my own dime since warranty is over. I thought there was at least the possibility that the piston inside the trans cover could be the culprit. So I bought a new piston assembly. It was only $35 or so. So no big deal if it didn't fix anything. It's too soon to know if anything will change with clutch engagement but I now know exactly why the fluid was changing colors and where it was coming from! Turns out there is a lube that needs to be applied to the piston and seals before installing the new piston in the bore. And wouldn't you know, it's a black graphite liquid lube! So now I know why the fluid gets dark and graphite looking! I still hold hope that the clutch engagement gets more consistent since the original piston had slight damage to the lip of the inner seal. Of course I have no way of knowing if the newly installed one might not now have the same damage since it's a bugger to get the piston/seal started. The seal flares out and must be compressed and "tucked" in to the bore. Fingers crossed that I didn't mess it up.

Too cold here for a test ride tonight. But I did bleed the line and check clutch operation in the garage. So far so good. Really not much of a point to this whole post but to maybe give someone else who has a hydraulic clutch an explanation for why the fluid doesn't stay clean and clear like the brake fluid does.

 

Humm that does explain while the bike was new I would see swirls of gray matter in the fluid and not any longer, I figured it was clutch material.....solves one mystery....thanks for the post.

 

He is talking about a hydraulic clutch and the hydraulic fluid. Not the primary.

Mark

 

Really didn't know that there was a HD with hydraulic clutch. My glide has a wet clutch that is cable activated. The primary fluid does get a greyish tint to it under normal operation from some clutch dust wearing into the fluid.

 

CVOs have the hydraulic clutch as standard equipment.

 

I changed to a hydraulic clutch several years ago on my '07 Road Glide. I "lubed" the piston bore with brake fluid just like I was rebuilding brakes. After all, that's all it really is.. I've never had any discoloring of the fluid, & after getting all the air out of the system the engagement point is ideal, & hasn't changed in years. Flushing the system results in slightly lighter colored fluid, but what discoloring there is I attribute to age. BTW, I consider the change to a hydraulic clutch one of the best mods I've done to my bike.

 

If in doubt do this test:
- Pump your clutch handle to have it engage soon then keep it in this position with a large rubber band.
- Measure the gap between handle and grip then check the gap a few hours later.
If all lip seals are in good condition there should only be a minimal change.

No moving seal can maintain a fixed pressure at a given position over a long period.

 

Thank you. I was wondering wtf was going on with my clutch fluid.

 

Every bike I've owned with a hydraulic clutch has done the same thing. The clutch fluid gets dark after a while but the brake fluid doesn't change color. I never figured out why. It must be brake dust but I don't see how it gets past the seals on the caliper pistons.

 

that's why i have a cable and intend on keeping it.