750ss dry clutch problems

[jerryz]

 750ss dry clutch problems
my 1991 750ss has dry clutch , recently the inner pressure plate had a crack in it , i managed to get a replacement from ducati even for such an old model , however the new pressure plate is slightly thinner on the surface by 0.5mm so requires one steel plate 2mm thick and shims under the springs according to ducati , but now the clutch drags and squeals ,slave is new , bled it , clutch master also fairly new , bled it more . still problems so measured the shims they are 0.8mm

just wondering if i should try 1mm shim washers instead

bike runs okay once moving just pulling away is nasty gearchange once under power is sweet

any ideas
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[Slide Panda]

If it's dragging, try the thinner shims.

[ducpainter]

If it's dragging, try the thinner shims.

+1...unless it slips at that point.

What I'd do to eliminate the squeal is clean up the steel plates with a scotch brite cookie on a right angle die grinder. It worked to eliminate the noise from my 900.

[jerryz]

Dry clutch 750 design very different from 900 dry clutch or other 750 wet clutch  models   , i have the thinner 0.79mm shims in now and it drags , i will clean up the steel plates and try the thicker 1mm shims s if i run it with out the extra steel plate it slips very badly , what i dont understand is why ducati could not supply the pressure plate to original specification then it would use no shims or extra steel plate and be much more simple crazy eh!!!!!!

[brad black]

by pressure plate you mean the plate that holds the springs in?  i don't see why the thickness of that would matter.  photo?

[jerryz]

No not that one Brad the inner pressure plate as it is called in the parts list I have  is the one with the 6 towers that the springs go over  , the replacement is about 0.5mm thinner

[ducpainter]

No not that one Brad the inner pressure plate as it is called in the parts list I have  is the one with the 6 towers that the springs go over  , the replacement is about 0.5mm thinner

Most people call that the hub.

What I don't understand is if you've accounted for the difference in thickness of the hub with an extra steel plate, and at the same time increasing the stack height by a little, why do you also need the shims.

Thicker shims under the springs will only make the dragging worse IMO.

Have you tried removing the shims?

[Dellikose]

That sounds like the clutch hub:

http://www.sprocket-one-racing.co.uk/ekmps/shops/dukedemon/images/ducati-clutch-hub-assembly-299-p.jpg

[jerryz]

Ducpainter ...the extra steel plate is 2mm thick without the shims the clutch drags like mad as the hub pressure plate is 0.5mm thinner than it should be  I have now added 1mm shims  so te clearence should be    about  right ? will test in the morning  , if that does not work i will try another idea???

[brad black]

#18 in this picture:

http://bradthebikeboy.blogspot.com.au/2013/02/750-dry-clutch-photo.html

so the spring posts are 0.5mm shorter?  i still don't get the 0.5mm significance.

[jerryz]

no Brad because the back hub plate is  approx 0.5mm thinner the spring posts are in effect 0.5mm longer  so if put together in normal form the clutch slips all the time , Ducati told me to add an extra plate which is  2mm thick  and then shim the posts to balance up all the extra thickness until it does not drag or slip its a PITA

I hope to test it again later today ....oh and to the question why dont they supply the part to original spec it seems that these old dry clutch 750 parts are reconditioned ones !!!!  and its probably been machined to remove some defect  hence the dimensions are not standard ,I am not happy because this was from a Ducati dealer and supplied from the factory stock .

[brad black]

afaik ducati wouldn't recondition anything.  no manufacturer does, it's way too costly.

it might be the wet clutch part.  if you put a 0.5mm washer over the clutch springs to preload them an exta 0.5mm it should be as was.  there shouldn't be any need to add plates.  0.5m is less than a pack wears.  have you measured it to confirm that's the difference?

sounds like something else is going on to me.  the new plate isn't hitting the inside of the hub is it and causing it to slip as was?

if you put a 2mm plate in them put 1.5mm of washers on the spring screws to let the hub sit back 1.5mm, which will also account for that.

a dry clutch 750 should run with 4 springs at most, i can't imagine one slipping.  i'm sure i've run 748 with 3 springs removed in the past.  and i have ridden a 1098 with only 3 springs - two posts were broken off, required an extra spring removed for symmetry.  only slipped a little at times!

makes a nice difference to lever effort.

[BastrdHK]

Would it be possible to shave/sand the posts down .5mm? 

I don't know anything about this bike, but would it be possible to use a 900 clutch hub/basket to eliminate this pain, or does your model have a different mounting assembly?

[jerryz]

yesterday I rode the bike over 70 miles varied riding  with the 1mm shims in its not slipping and not dragging , but a little grabby off idle in 1st gear which maked town riding and pulling away tricky so I will get some fine 0.2mm shims to add a tiny bit more lift today just to smooth it out a bit then it should be fine ,,,,the part is definitly from a early 750ss and my dealer says that they are re conditioned factory stock it even comes with  a note with fitting instructions in italian about the extra plates and shims ,

weird  but i am getting there