Need some master cylinder help...

[dus10r]

I have a Brembo RCS 19 clutch master cylinder. I tried for 4 hours today to bleed it and couldn't ever get it to bleed out. Then I noticed that if I pulled in the lever really quick the clutch would disengage but if I pulled in the lever really slowly the clutch wouldn't move at all.

I also noticed that if you pull the lever in quickly it will disengage the clutch AND as you let off the lever slowly it will slowly engage the clutch, BUT when the lever gets let out a certain distance it all of sudden goes limp, looses all of it's tension. But if you pull the lever in slowly before it gets to that let-out point it will slowly disengage the clutch like it should but if you let the lever out too far to it's "limp" point and then pull it back in, it won't do anything...

I've never seen a clutch do anything like this before. any ideas?

[nobody]

Are you sure its not the slave cylinder?

[MakisRC51]

I believe you should take both master and slave cylinders apart and service them. This is not something you overlook. It jeopardize the safety of both yourself and the bike's.

[dus10r]

Uhhh...that's why I'm on here... looking to see if maybe somebody else has had a similar problem and maybe knew what was the cause.

The slave cylinder is aftermarket and is a sealed unit, can't take it apart easily but it seems to be working fine.

The master cylinder is the new Brembo RCS 19 which I'm told can't be rebuilt, has to go back to Italy or something lame like that.

I just can't picture in my head what internally would cause that...

In my mind the piston either pushes fluid or it doesn't, I don't understand why it works quickly but not slowly. And why it would hold tension until it gets to a certain let out spot and then all of a sudden goes limp.

I assume that if it had a leak somewhere that there would be a visible fluid leak but there is not. But I do keep getting air bubbles when I bleed it. Which should mean in my mind that if air is coming in somewhere that fluid should be coming out but it's not...

[Kinetic Rider]

I had a similar problem with my 998, sometimes the slave/clutch would actuate normally other times it was as if no slave was connected at all. Bleeding it seemed to help but it still sometimes did not actuate the slave. I was always prepared to "fan" the clutch lever once; then, on the second pull it would work. Mine also never leaked brake fluid.

The problem was the slave. FYI, the push rod can spin the piston in the slave which damages the seal enough to cause the erratic operation. I tried putting more grease on the push rod end, it would work normally for a couple days but would always act up. Also FYI, the slave gets very hot & if the piston spins this is what causes the slaves to get damaged. I was going to buy an Evoluzione Slave because their slave has a bearing that the push rod rides against versus a stock slave which only has grease in the cup of the slave piston but instead I just bought a stock slave "take-off" for $20 as the blingers don't like the "look" of a stock slave. LOL

[dus10r]

Thats the slave I have...so I know it's not the slave. The slave is perfect...I took it off, cleaned it up. Pressurized it and it's holding no problem at all. I'm pretty sure this is Brembo RCS related.

[Old Fart]

Bleed the banjo fitting at the master? With an assistant, have him lightly pull the lever while you loosen the banjo until it leaks fluid. Tighten it before the lever hits the bar.

Still no joy? Perhaps there is a bit of crud on the master piston that allows internal leakage. Take the master apart and clean all the guts and give it another go.

[dus10r]

Okay...so just an FYI for anybody else with these Brembo RCS clutch master cylinders.

Not quite sure why they need to be sent back to Italy for rebuild. They actually come apart very easy and there's only a few parts to the piston and 2 small rubber wipes attached to it. If you had the parts these things would be a snapto rebuild. I wonder how different the parts are from the normal Brembo radial master cylinder...I lay money there isn't much difference as long as the bore size is the same.

But I digress....

So if you ever have the problem I mentioned do this...

1.) Loosen the screws securing the master cylinder to your handle bar and turn the master cylinder on the bar so that the piston that is pushed in when you squeeze the lever is pointing straight up. then retighten the master cylinder to the bar.

2.) Remove the clutch lever from the master cylinder. (1 bolt and nut)

3.) Pull the little protruding rod out from the rubber seal, there is nothing holding it in, it's not attached to anything.

4.) Use a very small flat head screwdriver and pry the rubber seal off from the edges.

5.) Using a pair of snap ring pliers grab the snap ring and remove and the washer behind it.

6.) Now what's left is the actual piston mechanism. Just pull it out but becareful theres a long skinny spring that it fits over...it could come out too when you pull it off...if not don't worry about it, it can stay in.

(This was my problem)

7.) Wipe any debris or dirt off of the piston and it's wipes and inspect for damage.

8.) If no damage, reinstall everything in reverse order.

(Note if you need to remover everything, the only other part is that long skinny spring, but when you go to put it back in it just doesn't sit in there, there is actually a little rod that sticks out at the bottom and the spring fits over it.)

So...my problem solved... dirt got in there somehow and was causing the wipe to not seal correctly.

[Old Fart]

Thought so. Glad it worked for ya.

Why send it back to Italy for a rebuild? American liability. You can't get rebuild parts for Brembo masters here but you can get them back door from other suppliers.

Gotta love the society we have created....

[Zillr]

disassembly and inspection is the only way to know where you stand w things mechanical. good call Old fart. I am an old fart too. I have on occasion replaced assemblies, but usually only after inspection. I just bought an 1199 and the frt master had same symptoms so I got the dealer to fix it. I did not inspect. They claim that Ducati sent a part overnight. Works well now.