750 Sport Clutch Cover and Slave Seal

discussion about the 750 Sport and '89/'90 900SS, which share many mechanicals with the Paso series
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deswoodau
Posts: 57
Joined: Fri May 02, 2014 10:08 pm
model: 750 Sport
year: 1988
Location: Australia

750 Sport Clutch Cover and Slave Seal

Post by deswoodau »

Just wondering whether anyone is having the same issue. After 10 years of ownership and only covering about 5000kms, the clutch slave cylinder o-ring looks like it's ready to start weeping again. Over the years I've twice replaced it with Ducati OEM o-rings but after a while starts seeping again. I hadn't bled the system for a few years so after bleeding the brakes today I thought about the clutch (then thought maybe just leave it alone)......anyway I bled it through to notice a minor seep of old fluid via the slave cylinder after bleeding it through. Very minor, but enough for a drop to roll down the pressure plate requiring a wipe.

A few years ago while replacing the o-ring I noticed some minor pitting in the slave cylinder clutch cover casting along the path of the o-ring which I suspect is causing pre mature wear and tear of the seal.

Two options I'm thinking:
1) Attempt to locate a new clutch cover. (Anyone out there?)
2) Try an aftermarket o-ring that's a little stronger\bigger (Anyone know of a alternative o-ring better than oem?)

As always, thanks to the Paso followers out there.
Mc tool
paso grand pooh-bah
Posts: 1883
Joined: Wed Dec 05, 2007 12:35 am
model: 906 Paso
year: 1990
Location: New Zealand

Re: 750 Sport Clutch Cover and Slave Seal

Post by Mc tool »

there is a mod that is basically fitting a later model slave piston assy with an oil seal instead of the o ring ( Im sure there is a thread on this somewhere here ..... maybe have a search ), and fitted a roller skate bearing to it .......I think
But , if you can see pitting in the cylinder wall that will damage the o ring ( Ducati dont make o rings so any good quality o ring is ok ) . You could get the cylinder sleeved ( now that Im awake I do recall making a centre button to go in said skateboard bearing out of a brass bolt :huh: ). You may also be able to use some new fangled liquid metal product to fill the pitting .....dunno much about it but they stick jumbo jets together with it.... and the space shuttle .... ( mmmm maybe they shoulda used Ducati O rings :lol: :lol: )
These clutches can be a proper bitch to bleed . I think it coz the internal dia of the clutch hose is big enough to allow the bubbles to keep floating up the hose against the slow pulsating fluid going down , anyhow I reverse bleed mine , air bubbles can hide in the banjo on the master cyl and sometime you have to take the cyl assy off the handle bar and hold it so the bubbles go into the cyl , sometimes you can get it by cracking that banjo instead of the bleed nipple
I wish I was young again............Id be heaps smarter than last time
deswoodau
Posts: 57
Joined: Fri May 02, 2014 10:08 pm
model: 750 Sport
year: 1988
Location: Australia

Re: 750 Sport Clutch Cover and Slave Seal

Post by deswoodau »

Thanks Mc. It's just another one of those quirks I guess and more hours engineering a solution. It looks like the seep\drip was caused by the bleeding process as there's no further leaking today however I'm yet to ride it. I'll ride it in the coming days and if there's no fluid I'll leave it alone as I'm sick of playing with it.
Having a perforated cover makes monitoring easy.

If needed I'll attempt to fix the pitting with an aluminium heat proof filler, lubricate and service the piston, new o-ring and pray for a miracle.

I'm not optimistic but it is an 80's Ducati after all.
Mc tool
paso grand pooh-bah
Posts: 1883
Joined: Wed Dec 05, 2007 12:35 am
model: 906 Paso
year: 1990
Location: New Zealand

Re: 750 Sport Clutch Cover and Slave Seal

Post by Mc tool »

Yeah , I think the clutch could do with a re-think ( he says 30 years after they actually did :P ). After one fits the modern slave cyl ..... or sorts the original ( its usually the bearing in the original that gives up )..... I been thinkin about the pressure plate and the spigot on it , and I think that shimming the clutch springs so that the pressure plate lifts evenly would be worth the effort . Shimming clutch springs is something that was vital to the correct operation in a lot of older bikes . I would love to see just how concentric the pressure plate is when lifted. I think that this is the reason that spigot breaks off ..... because its fighting to keep everything running true. When the pressure plate is lifted the whole thing is sitting between 6 springs and the clutch button , it doesnt take much thinking so see that if the springs are not all even then the pressure plate , springs and the clutch back plate have only that spigot to try to keep it running true . I also think ( ! Im on a roll now :lol: .... all this thinking ) that this has some bearing on the slave cyl wear too , I can visualise that piston rolling around the internal circumference of the cyl and quietly flaring out the open end ( re sleeve job )
TBH I dont even like looking at that pressure plate ..... looks real half arsed ( so we know its genuine :lol: ) if someone was to make a flash looking ally one Id be in like Flynn. Im thinkin that when they built the paso everyone forgot about the pressure plate untill they went to start it and then Giuseppe say " WTFa you guys wea got noa pressure platea" so they had to knock one up before the press got sick of waiting and went home :lol:
I wish I was young again............Id be heaps smarter than last time
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