Clutch slave piston health
Posted: Sat Nov 04, 2006 6:58 am
After all this talk about getting your clutch bled and such, I thought I would take off the clutch cover and look at that piston/throw-out bearing oddity that was in there. I looked at the picture in the manual and thought, there's no way all those parts are in there. But, I'm here to tell you, all those little parts are in your cover. And they probably haven't been treated very well, if they are anything like what I found.
If you haven't taken yours out yet, let me tell you its not that big of a problem. Just unbolt the cover, and pump the lever until the piston comes free. Be ready to catch the brake fluid that will pour out. The piston is steel, and there is a spring underneath it, but don't worry, it won't jump out. There is an O-ring seal around the piston. The problem with the design is that the piston is supposed to ride in the housing, but there isn't a seal to keep out water and grit. My piston was very rusted and pitted. Fortunately, the bore in the cover still looks great, and the O-ring still looks OK. I'm debating on how to seal that up better before I put it back together. Regular grease will mess up the o-ring.
Inside the piston is the throw-out bearing. This is a Ducati original, and a big reason that the whole thing got moved to the other side of the engine a few years later. Nice little bit of engineering, and surprising robust bearing for having so many bits to it. It certainly can't be cheap to replace one of these units. Once you get it out, take it to your bench to clean it up and repack with grease. Take the o-ring off so you don't get grease on it. There are handy flats machined into the side so you can mount it in the vise while you work on it. The seal is easy enough to pop off if you have one of those little hook ended pry tools. Getting the retainer ring out is a bit of a trick. Its simply a cut piece of piano wire. Get the sharpest, thinnest awl you have. Once those are out, the center bit lifts right out. Be careful, there are loose ball bearings in there. Take them out carefully, and clean the parts, inspect, repack with good moly grease and re-assemble. I didn't attempt to get the needle bearing cage out to clean. I just packed more fresh grease into it. Be careful not to get grease or oil on the o-ring. It will make it swell and become useless as a seal.
Apon bleeding the line, I found a bunch of air hanging out in the banjo fitting on the cover. I cracked that bolt, pulled the lever, and got lots of air. Then the system worked really well.
So, if you think your clutch pull is too stiff, or if you are hearing noises when you pull the clutch lever, it may be time to give this peculiar devise a visit and give it some TLC. While mine worked just fine, it sure looked ugly when I openened it up. If you have a vented clutch cover, you should probably do this on an annual basis. This is a good job for rubber gloves if you don't like brake fluid and old moly grease on your hands.
That's my tip for the week.
If you haven't taken yours out yet, let me tell you its not that big of a problem. Just unbolt the cover, and pump the lever until the piston comes free. Be ready to catch the brake fluid that will pour out. The piston is steel, and there is a spring underneath it, but don't worry, it won't jump out. There is an O-ring seal around the piston. The problem with the design is that the piston is supposed to ride in the housing, but there isn't a seal to keep out water and grit. My piston was very rusted and pitted. Fortunately, the bore in the cover still looks great, and the O-ring still looks OK. I'm debating on how to seal that up better before I put it back together. Regular grease will mess up the o-ring.
Inside the piston is the throw-out bearing. This is a Ducati original, and a big reason that the whole thing got moved to the other side of the engine a few years later. Nice little bit of engineering, and surprising robust bearing for having so many bits to it. It certainly can't be cheap to replace one of these units. Once you get it out, take it to your bench to clean it up and repack with grease. Take the o-ring off so you don't get grease on it. There are handy flats machined into the side so you can mount it in the vise while you work on it. The seal is easy enough to pop off if you have one of those little hook ended pry tools. Getting the retainer ring out is a bit of a trick. Its simply a cut piece of piano wire. Get the sharpest, thinnest awl you have. Once those are out, the center bit lifts right out. Be careful, there are loose ball bearings in there. Take them out carefully, and clean the parts, inspect, repack with good moly grease and re-assemble. I didn't attempt to get the needle bearing cage out to clean. I just packed more fresh grease into it. Be careful not to get grease or oil on the o-ring. It will make it swell and become useless as a seal.
Apon bleeding the line, I found a bunch of air hanging out in the banjo fitting on the cover. I cracked that bolt, pulled the lever, and got lots of air. Then the system worked really well.
So, if you think your clutch pull is too stiff, or if you are hearing noises when you pull the clutch lever, it may be time to give this peculiar devise a visit and give it some TLC. While mine worked just fine, it sure looked ugly when I openened it up. If you have a vented clutch cover, you should probably do this on an annual basis. This is a good job for rubber gloves if you don't like brake fluid and old moly grease on your hands.
That's my tip for the week.
Still wondering, that i have still that original "setup" in my 750 Paso and nothing bad in my system still, never opened and function still, like "trains toilet" :laugh: :laugh: :laugh: Btw, i have cleaned carefully allways that piston surroundings, when opened and cleaned my clutch plates with compressed air... (like dry clutch need to do quite often... 
) Maybe that is reason, that my piston function still very well, but surely one day have to open piston/sylinder... 
Anyway: THANKS!