Gentlemen:

I lost use of my clutch on my Saturday ride: I think the slave cylinder failed (pulling in the lever results in absolutely nothing but a squish sound from the item in question. Do Y'all think this slave from yoyodyne, available at Bevel Heaven, would be a viable replacement? Thank you in advance for your consideration and time.

https://store.bevelheaven.com/Engine-Re ... rs-DUCATI/

There are posts in the FAQ's detailing how to modify and fit a later type piston ( off a SS ) , bit of shagging about but a better set up in the end , oh , and the clutch is a proper bitch to bleed ( posts on that too ) That yoyodine cylinder assy is off an SS and Im pretty sure that wont fit the 750 Paso , but the piston is what you want . Some after market slave SS cylinders have a larger than standard piston , which wont fit inside the P750 clutch cover /cylinder . I cant remember off hand the standard dia but the standard sized SS one will fit . It comes with a proper cup seal instead of the ordinary O ring , and with a bit of cunning you can make/fit a better bearing /stud assy ...... have a look at the faq post on clutch slave mod and you will see what I mean

Thank you for the reply! I've reread the FAQ and I'll probably take screen shots of all the good info and pictures and head west to Munroe Motors/SF. Kieth, parts wizard at the shop (rides a mint Darmah) will be able to help me source what I need from a 91-97 900SS with his access to the linked inventory of the west coast Duc dealers. I will take my Nichols ventilated clutch cover off and take the measurements of the existing slave's piston and have a close look at the assembly. I'll get what parts I can obtain together and bring them and the Paso sans bodywork on down to Nichol's shop in Union City for their expertise in reassembly, possible machining of mushroom pin and bleeding the system. Thanks to everyone for the info and documentation on this subject. The forum is such a blessing! I'll report my progress.

I made the stud thing out of an 8mm brass bolt. I just cut it short leaving enough shank to fit thru the bearing and then put it in the battery drill and filed a bit of a dome on the head ( poor mans lathe )

all you need is this number: 19590023B and the bearing SKF 608-ZZ. That is the cheapest option. The piston is 26mm in diameter unless (!) your cover is not originally from a Paso but ie from a F1 so do check that first.

Thank you both very much. Good news and great information! I am fairly certain my Paso has a clutch cover from an F1. Again, I am so grateful for all the time, energy and comradeship that makes this forum a continual bright spot in my life as a Pasoist. Couldn't make things workout without y'all. :beer:

Is that good news?! Have you tried to find a F1 slave cylinder? What`s the diameter, did you remove it and if so could you post pictures?
According to the F1 parts catalogues there were three clutch slave pistons.
067516450 31mm diameter and no o-ring groove as that's in the cylinder (part not available anymore) #41
067016460 31mm diameter with o-ring groove (part not available anymore) #46
066516450 28mm no o-ring groove (Laguna Seca/same as on 85 Alazzurra 650) #49

I really hope your slave piston is not the big one.

I guess I spoke too soon, w/o a real understanding of the situation: I haven't been able to devote any time to disassembly just yet. I've too busy trying to find work and make a living. I'll get at it this afternoon and report back here a.s.a.p. Thank you for your help and your time! That certainly looks like my clutch cover...

just ondo those four bolts and check the piston diameter. If it`s 31mm (which I doubt) you should remove it to see which of the two types it is. If it`s 26 or 28mm it`s not necessary.

26mm diameter piston, ventilated Paso clutch cover by Nichols. Piston,bearing sleeve and mushroom pin all stuck together (#46, #37, #36 on Table 10 of the parts catalog). Any suggestions on how to get them apart? I am such a novice that I don't really understand what failed. Perhaps because they are the parts are somewhat fused together? There was no loss of clutch fluid before I drained the system to remove the piston. Thank you all for the kindly assistance. Thanks and praises!

If you have not lost any fluid and have a squishy lever I would say that the issue is in the pump ( master cyl ) and not the slave . If fluid arrives at the slave under pressure it will either move the slave piston , thus working the clutch , or piss out , so I would say fluid is no longer arriving at the slave cyl. If the rear seal ( at the open end nearest the pivot ) in the pump is shot it will suck air into the pump turning it into a squish and no longer a pump , and making it impossible to bleed

Hamish is right. What makes me wonder is how dry and clean the clutch cover and also the newspaper on the floor is after removing the piston. Where`s the fluid?
Clean the piston and check if the bearing runs freely and makes no scratching noise. The pressure pin still looks ok. If you want to remove it pull it out gently. It can be stuck due to oxidation or be held in place by the little air that can get inside the piston (like when pulling the plunger of a syringe while holding the tip closed). Check if the recess in the center of the pin is actually a clogged hole. If it`s not you can try to drill through the pin with a fine drill. Trapped air won`t be holding it back then and you can also spray some WD40 in it.
If the bearing scratches or is seized check if the cylinder wall in the cover is clean, has scratch marks or traces of black rubber. A seized bearing can cause the piston to rotate consuming the o-ring.
If the bearing is shot you can try to remove it but that`s quite difficult w/o damaging the piston.

Thank you again to both of you for your kindness and all the help. So valuable and so enlightening. My master cylinder is from a '93 888SPO I'm told. To follow is a photo. There were no leaks at the slave cylinder, the bleed valve, or at the banjo bolt on the clutch cover. When I pulled the piston out to measure the diameter and inspect the spring and o-ring, I was careful to catch the fluid mostly in a container, thus not much mess. It sounds like things are pointing to the master. I will further inspect the piston, bearing and pin as per your suggestions. As long as the pin moves up and down and spins w/o friction or drag, should I assume the bearing is good? The cylinder looks really smooth w/o scoring or scratches, the piston is a little less pretty: though more discolored than scarred. the movement of the one inside the other feels silky. Perhaps I should source a new o-ring as a matter of maintenance?

Update on the inoperative clutch: It was indeed the master cylinder. It has been rebuilt and a new o-ring installed in the slave cylinder. New fluid and well bled. Works a treat, but just a little squishy- not as firm as hoped. I think I will finish the work with a hose and call it done. Thanks again for all the help and for your patience with me.