1991 750ss clutch problems

[jerryz]

 on my 1991 750ss ,the dry clutch version with the slave in the left hand case , new friction plates new clutch pressure plate and basket , new Master cylinder and slave piston seas l all bled by suction syringes , so no air in the system at all , lever is firm

well i have done about 150 miles of mixed riding and its still dragging and juddering off idle pulling away from standstill, and making twittering noses when using clutch to change gears on the move ,, also clutch action gets progressivly heavier once the bike is hot ,, tried different plates and stack height no change or improvement any ideas or will it eventually bed in ..i have fixed 4 previous later model ducatis clutches and never had issues like this .
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[koko64]

Do you mean slave cylinder on the sprocket side (LHS) or in the clutch cover side (RHS)?

I was talking to a 750 Elefant owner. His motor had the dry clutch with slave in the clutch cover ('88 model). He said that a dragging clutch with this design was common and neutral hard to find. The problem may be the master cylinder ratio was designed to not be too heavy, and pumps only a marginal volume to activate the slave. If the whole clutch set up isnt spot on, or nice and worn to the point of slipping, then it will drag. The plate composition of these clutches seemed to change alot each year in an attempt to fix this.

I was wondering if another master might give more margin and a longer clutch "throw".

Not very helpful, but might spark some ideas.

[jerryz]

its  an in the RHs case slave , i have a new 13mm handlebar master as well and all new plates and springs and clutch centre ,new braides ss hose , its working now after 38 dissasemblys , bleeding and retests , and mixing up the stack of plates  and plate thickness but it is still a little grabby and squealy noisy at idle when clutch pulled in  ,, i will run it for a while and see if it beds in .jeez what a saga    .never had a problem with any ducati clutch before like this but all my other dukes are LH side slave models .

[ducatiz]

Old style clutch.  But you've got an oddball model, the 750ss went to wet clutch only after 92..

There are about 6 generations of pistons in this.  Some have the oring in the bore, some on the piston.

There is a bearing and a brass "mushroom" in the face of the piston which acts against the clutch on engagement.

The bearing wears out. It's not hard to find the bearing, but it's a pregnant dog to remove.

The bearing allows the mushroom to turn and when it starts to wear out, it causes the piston to rotate in the bore (bad) and can drag the clutch.

Good news is that it's easy to remove and replace the seal.  Try that first, but my guess is that it is turning in the bore and dragging the clutch.

If you pull the piston, post the pic and dimensions and I'll get you a link for a new seal (or two, some had two).

Here are some of the RHS dry clutch pistons I've collected... 26mm, 27, 28, and 31 mm.  I am curious which version you have. 


The three on the left are bearing side up, with the mushroom installed.  the F1 piston 31mm on the right is bearing side down showing the indent for the helper spring.

[jerryz]

Ducatiz,,, sorry  a misunderstanding the bike has a dry ckutch ,, i have recently had the piston out of the casing and replaced the seal? oring and the bearing in the piston moves freely tthe mushroom/pushrod is also in good condition ...I am travelling overseas  now but when back in Uk March  will dismantle those parts again and recheck 

Oh and  from memory it is not like any of the ones in your photos  it is completety flush on the face with the mushroom  no lip at all , the back end with the spring is the same as photo  ?

cheers jerry