Slave Cylinders

[ChrisK]

Educate me on clutch slave cylinders. I suspect mine is going bad, because it's impossible to bleed the line (sounds like air is being let in at the slave cylinder) and the clutch pull is super hard.

So, my question is: are clutch slave cylinders pretty much universal across all Ducati models? If they're not, how do I tell which ones will fit my 98 M900? Basically, I don't want to shell out the cash for a new aftermarket one, and I'm hoping I can use one from a newer model Ducati?

[freeclimbmtb]

Educate me on clutch slave cylinders. I suspect mine is going bad, because it's impossible to bleed the line (sounds like air is being let in at the slave cylinder) and the clutch pull is super hard.

Hard to pull clutch doesnt sound like a bad slave to me...maybe binding on the push rod or something... 

Now if you pull the clutch in and it slams into gear and lurches...I would say bad/air in the slave. 

Also, air compresses, hydraulic fluid doesnt, so a hard pull would point to no air whereas an easy pull would point toward air...

As for bleeding it, i put a piece of clear tubing over the bleeder and into a jar, and just do the old reliable: pull the clutch, crack the bleeder and reshut it, release the lever, refill the reservoir, repeat.  ive had good luck bleeding clutches...not so much bleeding ABS rear brakes...

Another good tip is to back the screw out quite a bit, put petroleum jelly or a heavy grease on the threads, and screw it back in before you start bleeding, air will actually seep in through the threads, grease keeps it sealed up.

[ChrisK]

Yeah I guess I agree about a hard clutch pull sounding more like binding on the push rod.

I also do the "old fashioned" method for bleeding the clutch, and no matter how long I do it, the amount of air bubbles coming through into the tube doesn't decrease. I will try the grease method you suggested, to see if it's seeping in at the threads. I would also like to take it all apart and examine the push rod.

Of course, those two things might have to wait a few days, because I'd like to wait until the riding season is OFFICALLY over for me (I think I might have one more day).

[freeclimbmtb]

Also, air in usually means fluid out.

Pull the three cap screws off the slave and pull it and look for signs of leakage.  Should take you all of about 10 minutes and shouldnt impact your riding season at all. 

Another tip:  air floats right? pull the slave and as much hose as you can and try and get it higher than the master.  if you cant get it that high, then just rotate it so the bleeder is the highest point of the slave and bleed it off the bike.  (Not being attached makes bleeding tricky though since you dont have the clutch springs pushing back...ive used a bolt in place of the push rod, and a quick clamp to keep pressure on it...if you do that method you definitely need another set of hands though...)

Im jealous of your riding season though...ive been done for more than 2 months...

[ChrisK]

freeclimbmtb,

That one last day of the riding season would be tomorrow, after that the forecast looks pretty bone-chilling. So I should be able to get to this soon.

The bleed screw is already at the top of the slave. But yeah, I might take it off and see if I can notice anything happening on the back side.

Also, I tried asking this on another thread but never really got a straight answer. What all is involved in checking out the pushrod? I've never taken it, or anything like it, apart before. Do I basically just take off the pressure plate and clutch plates, then slide the pushrod out the slave slide of the bike? I feel like it has to be more complicated than that...