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Discussion Starter #1
I seem to have developed some slack in the clutch lever, manifesting in a clutch engagement point far too close to the clipon.

Bleeding from the clutch slave didn't help. I traced it to air in the reservoir end of things. I managed to get the air out by adding some now low fluid and pumping the lever. All good now at this time.

Since it slowly manifested over time I wonder if it may come back. I'll have to wait and see. I did some searching here and there is a rebuild kit with seals. Any thoughts?
 

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If you have the reservoir topped off and you get more air into the system, you need to rebuild the master.

Based solely on your description, you may have not bled the slave long enough to get all the air out, and that may be something that you still need to do. If you are very careful, you can also bleed some at the top banjo, just be careful that you keep the fluid away from paint and plastic.
 

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Do yourself a favor and pull the slave cylinder off as well and give it a good claening. They get gunked up and start causing issues. Mine was pretty bad when i pulled it apart. Depending on how everything looks, may be worth it to replace all the seals and gaskets.
 

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Discussion Starter #6
Clutch fluid was replaced in spring.

The slave is fine. I double checked with a rebleed when diagnosing the issue.

No visible leaks anywhere that I can see.

Topping off the reservoir is difficult. It is at such a steep angle with the tilt of the clipon (to get the levers facing at a comfortable angle downwards). The actual fluid line is at a very different angle than the full/empty lines on the reservoir. It does look like by bouncing around that it could draw in some air because of that, but IDK

I had some bad caliper seals on on the bike when I had it. So it maybe needs a rebuild too.

I guess the only way I will be able to tell is over time. If it is air ingress it is slow, as in weeks. Unless you have other thoughts.
 

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When you're topping off the bottle, you should lose the bolts that hold the master and turn the steering so that the bottle's cap is as much parallel to the ground as you can. After tightening the cap, you can adjust it back to the position it fits you the best.

It would be a good idea to pull the slave's piston out and check the seals. Not that hard of work like the calipers. Starting on the easy, to inspect, end, if it checks out ok, then you disassemble the master.

When you put the piston on the slave back in, pour some fluid inside first and then push the piston in so that fluid is pushed in the bottle. Makes the bleeding wayyyyyy more easier ;)
 

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I can add a couple things, I've had some bleeding issues too.
As you already suspect, maybe your master cups/orings are beginning to give out a little.
I'm betting you already figured out about turning the handlebars to the appropriate position, but after that, I've had to follow the line downwards and make sure there are no high spots in the rubber line that connects to the hardline. That one drove me batty till i figured it out.
Have you detected any sign of leaks around the master?
 

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Discussion Starter #10
No leaks detected.

Ya, I've always done the basics to fill the reservoir. Still, I went back and made the extra effort to fill it more a few days back.

As mentioned, I fixed the slack by working on the reservoir end. Now I have to see if it comes back. The bike wasn't being ridden much at all when the slack appeared. But imo it could have happened either from an improperly low reservoir that let air air when I used it, or a slow ingress of air from worn MC components (seals). I guess time will tell.
 

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If the fluid level is low and you turn the steering, it is very plausible to pump air in the system by accident if you pull the lever at that point.....

Since this system's fluid doesn't heat up like the braking system, it's no harm to put some extra fluid in the res to be sure.

I prefer to fill it up (when it is aligned parallel to the ground) up to the point that meets the rubber inside. No air gap between them. But when I do this, I have always removed the slave and pressed the piston all the way in and hold it there until I am done with filling the fluid up, bolt the cap on the res and everything.

Then I release the piston, which makes the fluid drop its level in the bottle, but sucking the rubber along with it as well.
This way the rubber works as a heat expansion absorber for the fluid in case it's dilated by heat, but still no air in the reservoir whatsoever.

Hope this helps buddy :)
 

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Both my RC and CBR1000 have suffered from this problem. It seems partly related to a lack of use but I can't say for certain. I also noticed that the clutch fluid would darken over time so that may be related. Even fitting a radial master cylinder didn't help and the only solution was a period (6 months or so) bleeding of the clutch. Not a big issue really and it always came back to normal afterwards.
 

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Discussion Starter #14
Finally took the bike for a quick ride since fixing the slack in the clutch. It is now the complete opposite. It engages the clutch so early in the pull you don't need to grab much lever at all. From one end of the spectrum to the other.
 
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