Hey all. I've searched and tried every technique on here. I keep losing clutch pressure, though I'm not leaking any fluid because each time I check my master cylinder, I see the same amount is still in there. I'll bleed until no more air comes out of the line, run the bike for an hour, and the clutch fades to nothing. The last trick I am trying is keeping the lever pressed in overnight and hopefully that fixes it.

I've noticed no signs of fluid leaking. Though once I replaced my clutch plates, this all started happening. I have reason to believe the clutch master is no good, as I notice that when I am driving, I can see a spray on fluid on my left mirror. Rather than spending the money on a new one from eBay, I pulled one off of my parts bike that I'm still rebuilding. Same issue even after bleeding it.

So is it safe to say I need a new clutch master and should I just go ahead and replace the line with a new stainless steel one?

Thank you!

Dustin, if you're absolutely sure you aren't losing any fluid, it can only be the internal seals in the master cylinder. A leak at the slave cylinder, or a leak at one of the hose connections would give similar symptoms, but with a loss of fluid.

Air in the lines will also cause a similar symptom, except you imply you've bled them well.

Two things to try:

Protect the area around the hose connection to the master cyl, and crack the banjo bolt loose. Squeeze the lever slowly, while loosening and then tightening the banjo bolt. This gets the air out of the connection that sometimes cannot be gotten any other way. (An alternative is to buy a banjo bolt with a bleed screw in the end of it).

If that doesn't cure your problem, take the master cylinder apart. (I don't have a stock Paso master cyl on my bike, so my advice can only be general in nature). Once you have the lever off, and pin removed, you use a set of internal circlip pliers to remove the circlip. Remove the internals, and take a picture (so you can verify the orientation of any parts later). I bet you'll find, like on the one I was working on today, that the piston seal is fine, but the O-ring is swollen or cracked.

Rebuild parts are no longer available from Brembo. At least that's what I found with my Goldline MC's. Parts are available from places such as Bevelheaven. Or, if all you need is the O ring, just buy a Viton O ring of the appropriate size. That's what was wrong with mine.

Here is a photo, where you can see the O ring was so swollen it wasn't keeping a good seal on the piston:


Don't match the old Oring to get the size of the replacement. Remember, it has likely swelled. Bring the MC piston, and have them match that.

On a side note, I think it is absolutely absurd that Brembo isn't selling rebuild kits anymore!

Thanks delagem! I went out and leaned the bike far over as I could, took the cap off, and slowly squeezed the lever and to my surprise no air bubbles came out. So I cracked the banjo bolt, slowly squeezed lever, and 1 tiny air bubble (I mean miniscule) appeared. Now I don't have great pressure, but I can hear the piston engage and disengage better. Test drive over to the shop tomorrow as I need to get her inspected. I'll update after tomorrow happens.

Again thank you!

You might find to get all the air out you will need to remove it and point the lever at the sky then give it a pump or 3

I managed to get the air near the master out by removing the whole clip on, pointing the lever up and blowing (with my mouth) part of the fluid in the bleed line back in to the slave cylinder. While doing this i could hear a small squeak of air escaping out the master cylinder. you can also pump some fluid back with a big syringe, brake fluid tastes awful, I can tell you!

I can't believe the set up for the bike, never thought it would ever be this difficult. Just got back from work, no time yet to take the bike out as I have to go workout. Once I get back I am going to pump about 3x and do a quick bleed, then take it for a ride. Be back on here later tonight with either good news or bad news!

I ended up putting the lever straight up and down, and had success bleeding it that way. I know this is in fact a great setup, just was so annoyed and tired after work, haha!

So yes, the clutch is currently working and a test drive showed it to be stronger than ever. If I slowly lose pressure again, I will know to take the master apart and replace that o-ring. Appreciate all the help you guys have given me!

Couldn't do it without everyone from this site

I had a shit of a job bleeding my paso clutch too . In the end I pumped fluid in via the bleed nipple on the slave cyl and forcing the fluid up into the master cyl res . There is a mod that involves fitting a piston ( slave ) from a later ducati ( posts are here ) thats worth thinking about

So I found my other clutch master cylinder and decided to see the problem for the leak.

Here's the first picture of it spread out:



That's the order that things came out, no springs or anything else. My concern is that there is no o-ring on the slider/pivot arm.



I'm assuming there should be an o-ring on there? While it rains right now, I have something to work on. Then I get to pull apart my parts bike till the rain lets up. Want to tear into the transmission because I believe the bearings need to be replaced (grinding noise when it moves and reason it was sold was due to the trans going.)

Oh, boy! There's a whole bunch of parts missing! Good thing you have a spare to use... Look at this photo of a section of the parts microfiche, all those parts listed under #3 are supposed to be in there.

Download the microfiche and service manual from the stickys above, if you haven't already.



(Edit: changed the picture from the microfiche, had previously posted the brake master cylinder by mistake)

Oh my... I am missing a massive amount. Could it be that this clutch is a different one from factory? It is brembo and to my knowledge this one in the picture was the stock one. I had taken this one off the bike and swapped it with my spare. I am amazed, time to start looking for the rebuild kit!

Thanks delagem!! And yes we will have to ride one of these weekends, my brother almost has his bike finished (93 kawi 500 ninja, his first street bike and wasn't a bad 400$ investment).

Couple confirmatory comments: last time I had to bleed the clutch, the same fade issue occurred and no matter how many times I thought I had all the air out, the same issue recurred. I finally resorted to sage advice elsewhere here and pulled the left handlebar completely off its mount and elevated the fluid reservoir higher than the banjo bolt on the reservior and wala, one bubble burped out! Problem cured.

Previous to this, I rebuilt the clutch master cylinder with exact Brembo replacement parts in a rebuild kit I bought from www.bevelheaven.com. Give him a call if you need advice; great guy. From your photo, there's a whole lot missing from the m/c.

Thought this might help too. Pretty sure its the guts of my clutch master cylinder (might be one of the brakes) but it shows the different parts involved which are generally all similar.