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Clutch Slip

Discussion in 'Technical Help' started by Cream_Revenge, Mar 11, 2017.

  1. Try putting the old slave back, measure how much the original pack opens up with the old slave and try and replicate the lift height with the upgraded slave fitted.

    I have two bikes fitted with slipper clutches and uprated slave cylinders and neither gives me any trouble beyond the normal pulse and judder I would expect of a slipper clutch.

    Replacing the spider is going to exert more force on the hub and therefore this could have changed the way the clutch has been reacting in the past. In theory it should have no effect until it needs to slip, but something is clearly not operating smoothly enough to have the clutch working as it should.

    One trick that some use is to use more than one dished plate so that it causes the clutch pack to split more evenly. The order of the clutch pack plates does or can influence the how the pack splits when the clutch is pulled in, so juggling the order may help. I have done this in the past and it did make a difference for my purposes.

    Also check for any plates that may unlikely have become warped
     
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  2. Ok, how's this.

    Assuming it's because the inside pushy bit of the new slave is slightly pushing on the rod causing the pressure plate to not sit tight enough on the plates. Could I put a thin 1/2mm washer between the clutch slave and the engine casing on the 3 bolts that holds the slave in place. That would move the slave slightly away from the pressure plate and I can remove the steel I added yesterday.
     
  3. I think you're creating a problem to cure a problem doing that , just do it correctly.
    Steve
     
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  4. Did you buy this slave cylinder as a new item? If not does the cylinder have the pushrod extension fitted inside it, in which case depending on pushrod length fitted to the bike you might be causing the mushroom shaped lifter to be putting pressure on the clutch pressure plate.

    There are two clutch pushrod lengths and dependant on that you then put in the spacer into the clutch slave to get the correct length.

    The easiest way to tell is to strip the clutch and check the centre mushroom lifter to make sure it is seated fully home.

    It sounds like something is not quite right here and it is advisable to go through the whole clutch setup including how the slave is fitted and also the pushrod to determine what is wrong.

    Pushrods do actually break so you might want to check that the rod has not broken.
     
  5. The only advantage of doing this would be to determine if this is where the problem lies.
    Shimming in this way would of course mean less lift at the pressure plate, so more drag...
     
  6. Slave was new. I've not fitted the extra bit that came with it.
     
  7. Have you checked the pushrod length? If it's an Oberon one then I think the instructions state the length of the rod, or they certainly give some detail on when to fit the spacer.

    If all the above seems to be in order then the next step might be to look for burrs on the clutch hub and the outer clutch bell, burrs (may) cause the clutch to hang up and affect the operation. After that check the seating and sliding of the clutch plates on the hub or within the clutch bell.

    Presumably the friction plates do have all the tangs correct and not notched or damaged.

    Did you fully bleed the clutch slave and use new fluid?
     
  8. Easy test to check this :- get access to the three slave cylinder fixings and undo all three for 2 complete revolutions. Apart from (if normally clean,uncorroded and un-gritty) the screws feeling slightly tight as they continue to undo, look carefully for a gap between slave and crankcase casting as it pushes/doesn't push slave away from engine. You could even grip the slave in your hand and see if it is 'sloppy' and if you can freely re-seat it on the crankcase casting.
     
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  9. [​IMG]

    That's the spacer. If I put that in it would push the plate away causing constant slip wouldn't it?

    New clutch fluid.

    It's a "factory racing" unit.

    Everything was peachy before the slave was fitted and I put her away for winter.
     
  10. 2 turns out on all 3 bolts. To push the unit back against the engine case needs pressure. I assume the weight of the fluid is pushing the pushy bit.
     
  11. Stack height.
    37.4 with extra plate.
    35.4 without. As it started yesterday.

    None of the steels seem dished and I can't see a mark on any.

    About 1/2 are 2mm and 1/2 1.4mm
     
    • Disagree Disagree x 1
  12. From Ducati.Ms


    The flat metal plates come in stock 2.0, 2.5 or 3 mm thicknesses. When the overall plate stack height wears say 0.5 mm, replace one 2.5 mm flat plate with a 3 mm one. At 1 mm stack height wear, repeat for a second flat plate. At 1.4 mm–.6 mm wear, replace all the friction plates. Allowable friction plate wear is 0.2 mm (each).

    There are a number of equivalent stacking methods:


    748, 916, 996 (From the Haynes Manual)

    7 friction plates
    1 convex plate

    2.0 mm flat plate
    2.0 mm flat plate
    3.0 mm friction plate
    1.5 mm convex plate (convex side facing outwards)
    3.0 mm friction plate
    2.0 mm flat plate
    3.0 mm friction plate
    2.0 mm flat plate
    3.0 mm friction plate
    2.0 mm flat plate
    3.0 mm friction plate
    2.0 mm flat plate
    3.0 mm friction plate
    2.0 mm flat plate
    3.0 mm friction plate
    2.0 mm flat plate
    pressure plate (line up marks)
    38.5 mm Total

    916SP, 916SPS, 996S, 996SPS

    8 (thinner) friction plates
    2 convex plates

    2.0 mm flat plate
    1.5 mm convex plate (convex side facing outwards)
    2.5 mm friction plate
    1.5 mm flat plate
    2.5 mm friction plate
    2.0 mm flat plate
    2.5 mm friction plate
    2.0 mm flat plate
    2.5 mm friction plate
    2.0 mm flat plate
    2.5 mm friction plate
    2.0 mm flat plate
    2.5 mm friction plate
    2.0 mm flat plate
    2.5 mm friction plate
    1.5 mm flat plate
    2.5 mm friction plate
    1.5 mm convex plate (convex side facing inwards)
    pressure plate (line up marks)
    38 mm Total

    998 (From the Ducati Service Manual)

    6 friction plates
    1 convex plate

    2.0 mm flat plate
    1.5 mm convex plate (convex side facing outwards)
    2.5 mm flat plate
    1.5 mm flat plate
    3.0 mm friction plate
    2.0 mm flat plate
    3.0 mm friction plate
    2.0 mm flat plate
    3.0 mm friction plate
    2.0 mm flat plate
    3.0 mm friction plate
    2.0 mm flat plate
    3.0 mm friction plate
    2.0 mm flat plate
    3.0 mm friction plate
    1.5 mm flat plate
    2.5 mm flat plate
    1.5 mm convex plate (convex side facing outwards)
    pressure plate (line up marks)
    38 mm Total

    Difficulty finding neutral is a result of an inadequate separation of the plates caused by air in the hydraulic line and/or installation of a too large diameter aftermarket slave cylinder.
     
  13. Had that been a Bucci style slipper, your stack height would be 36.5mm max but I have no experience of the STM type. Do you have aluminium synthetic or organic friction plates ? Again for the Bucci style, the steel compression plates are either 2mm, 1.5mm or 1.5 dished and in a (1098) aluminium friction plate pack you get 7 plates. I have often made the pack up with 1.5mm dished plates either side of a friction plate and finish with 2 steel compression plates. Unlike Red998, I have no problems with the older 748R 3 ramp steel slipper which I run on the 748R and 853 but I hate the 6 ball and ramp aluminium OE 1098R slipper which has all the graunch and shudder in 1st gear. I am sure you will get it sorted. Andy
     
  14. How about doing the same thing on your 999, so you can compare the feel of both.
     
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  15. There you go, remove a 1.4 and fit a 2 and you will have 36, half way between the two.
    Steve
     
  16. Just a few questions ...... the bike had no clutch slip when you last used with orginal slave cylinder ?

    Why would changing a slave cylinder affect the clutch basket height or operation ?

    Like has already been said ,if you put a bigger slave cyl on you get an easier lever pull with the down side of getting less slave cylinder travel which then can cause clutch drag issues as the plates do not seperate enough .

    Again if there was no clutch slip BEFORE clutch cylinder fitment why would fitting a cylinder affect this ??
     
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  17. Problem
    Thing is, the waters are muddied because other things have been done.
    The spider has been replaced and the ramps have been greased. Could grease have got onto the plates??
     
  18. Sometimes there are small manufacturing differences between slave cylinders and particularly aftermarket versions making it more likely for pushrod to 'bottom out' I think is what Creamy was thinking, I know it's possible when a combination of (usually aftermarket) clutch components add up to push tolerances the wrong way. Another test would be to refit old slave just to compare.
     
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  19. Arrrr yes, sorry old rider just skimming through , yes muddier waters .

    So different spider could of altered clearances
    Yes grease on friction plates ?
    Friction plates gone back in in wrong order and not bedded down to one another ?

    So Cream , when you have a clutch drag issue you also have a slipping issue .....or can you get it so you have drag but no slip ?
     
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  20. I assume you did put the balls back correctly in the hub?

    If I had this trouble I would start all over again and check everything in the clutch train, clearly an element or elements have been disturbed enough to cause problems.
     
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