Clutch Slave cylinder failure!

Discussion in 'Crazy-Awesome almost Dakar racers (950/990cc)' started by gefr, Oct 7, 2006.

  1. gefr

    gefr Life is a trip

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    Two problems could produce the failure of the slave cylinder!!
    One is the crack developing at the bottom of the piston!! just under the steel ball. This crack, minor as it seems, could open under pressure and leak the clutch liquid!! The clutch pressure is transmitted through the piston on to the steel ball and then to the push rod.

    <a href="http://s1068.photobucket.com/albums/u441/gefrago/clutch%20slave%20cylinder/?action=view&amp;current=KTMfotos214.jpg" target="_blank"><img src="http://i1068.photobucket.com/albums/u441/gefrago/clutch%20slave%20cylinder/KTMfotos214.jpg" border="0" alt="Photobucket"></a>
    #1
  2. gefr

    gefr Life is a trip

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    This is how it looks from the outside!! Read about this crack in an older thread on this forum!!

    [​IMG]
    #2
  3. gefr

    gefr Life is a trip

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    base of the slave cylinder!! This even though doesn't seem very important, works as a guide for the movement of the piston. So if it deforms, it could offset the piston so it will leak!! I plan to replace the base of the slave cylinder with an aluminum one to avoid the distortion produced by excessive heat!!

    [​IMG]

    and a solution

    [​IMG]

    [​IMG]
    #3
  4. kkug

    kkug Been here awhile

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    Thanks for posting the pictures. Thats exactily how my piston looked.

    Good tip on the plastic base for the slave cylinder. So you made a Alum.
    one from scratch??? or just replaced it with a new one?
    #4
  5. gefr

    gefr Life is a trip

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    I will have a workshop built the alouminum one for me next Monday. It will cost close to 70Euros, while the new part is warranty or if purchased costs 140Euros. I think though I am going to resolve this once and for all! I have also ordered the piston made of bronze! Slightly thicker and stronger. In the meanwhile, I am wondering if oil from the chain lubrication is entering the gap which developed and is harming the o-ring of the piston??? Someone here wrote he changes the o-ring occasionally because it turns rigid and brakes!! It is supposed to work with the clutch liquid which is mineral oil. So if it gets rigid, either the o-ring is not right material or the oil is not compatible!! And since some motor oil is getting in there, through the push rod, the o-ring could get harmed!!
    #5
  6. union jack

    union jack Mis-Adventurer

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    In answer to your question I use cheap o rings bought ten at a time. They are slightly thicker but last longer than the KTM items. Either way when I pull them they have all gone hard, and I use the proper hydraulic oil. I've found the Putoline clutch oil lasts longest. I think the biggest problem is the load and heat the cylinder and oil is subjected to. The 990 Super Duke uses the same Magura Slave cylinder but I have not heard of the same problem on these. The big difference is they use a Brembo radial clutch master cylinder with a bigger bore and reservior. Could the cure be a change to this set up?
    #6
  7. gefr

    gefr Life is a trip

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    I am sure if the heat plays a role in toasting the o-rings, the Super Duke keeps the motor cooler since it is more exposed and so more easy to radiate heat!
    As for the master cylinder, I wonder what the cost would be like?? I have to check the spare parts catalogue!!
    Cheap o-rings?? Aren't the vitton the best?? Did you ever try some of those?? Since changing the o-rings keeps you liquid tight, you do not have cracked slave cyl piston!! Never??

    Great info!! Thanks a lot!!
    #7
  8. union jack

    union jack Mis-Adventurer

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    Fortunately I've never had to replace anything other than the O ring which usually lasts about 9000 miles (got plenty of spares). What are the vitton type? It is the second slave though which was replaced at 10000 miles under warranty by the dealer so I don't know if that had more damage. Magura do a compact radial clutch pump (the 195 range) which is about £190 not including the reservoir or mirror perch. The Brembo version icosts about the same but is bigger, not a problem if you lose the hand guards. The only other thing to think about would be remounting the choke lever. A bit of butchery required. Might need a new clutch line with a 90 degree end. A piece of piss really, you first!:D
    #8
  9. Bartman

    Bartman SnowDog

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    So where are you getting the o-rings? I may try that before replacing the whole unit as I can't detect any crack in the piston.

    Thanks
    Bart
    #9
  10. union jack

    union jack Mis-Adventurer

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    Just got a selection from my local car accessories store. Got it well practised now. I can do a complete change in half hour.:D
    #10
  11. YOGOI

    YOGOI Prick

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    From the looks of this pic. The red dust on your sprocket means that your sprocket is wear'n on the shaft. Check the tourqe on your sprocket nut. The washer tab keeps the nut from coming all the way off, but the nut can still loosen somehow. I have been able to turn mine with my fingers before. Maybe this plays a part in the damaged cylinder.
    #11
  12. Lockers

    Lockers n00b

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    Same thing happens on the Super Duke with the clutch slave cylinder... I've just had my slave cylinder assembly replaced under warranty. Replaced the o-ring at 8000km, then the assembly at 14,000 cos it did it again.
    #12
  13. union jack

    union jack Mis-Adventurer

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    Oh great, glad to hear we're all in the same boat then! :baldy

    Did hear Aprilia have the same problem on the RSV and a American company Evoluzise or something make a replacement billet item. Perhaps we should camp out on their door step and demand the same service.
    #13
  14. johnnyg

    johnnyg Adventurer

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    Union Jack,<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:eek:ffice:eek:ffice" /><o:p></o:p>
    <o:p></o:p>
    Right on!!! The Evoluzione folks have a real good reputation in the Aprila community.<o:p></o:p>
    They are located in <?xml:namespace prefix = st1 ns = "urn:schemas-microsoft-com:eek:ffice:smarttags" /><st1:place w:st="on">Southern California</st1:place>.<o:p></o:p>
    <o:p> </o:p>
    38580 celine cove
    suite b
    murrieta, <st1:State w:st="on"><st1:place w:st="on">california</st1:place></st1:State> 92562<o:p></o:p>

    phone - <st1:phone w:st="on" phonenumber="$6639$$$" o:ls="trans">951.639.0967</st1:phone><o:p></o:p>
    www.evoluzione.net<o:p></o:p>
    <o:p> </o:p>
    With the increase in the number of 950s in the states, they may be interested in starting up a parts line. <o:p></o:p>
    <o:p> </o:p>
    What we need is to have a So Cal. 950 rider, preferably with some experience with the clutch problem, go in and talk to them and tell them about this web site (and other KTM rider sites), so they can do there own homework with regards to a potential client base.<o:p></o:p>
    <o:p> </o:p>
    And while we are at it. Maybe they can come up with a better water pump shaft and seal combination.<o:p></o:p>
    <o:p> </o:p>
    JohnG<o:p></o:p>
    #14
  15. K2m

    K2m ....58....

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    Neither could I, but after attacking it with epoxy on both sides it stopped leaking:huh
    #15
  16. gefr

    gefr Life is a trip

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    The nut is moving freely a slight bit!! It cannot move a lot because of the washer tub and I don't see any hazard there since the sprocket has receses and is secured on the axle! but the red dust you point out could be metal wear of some part...
    Thanks a lot!!
    #16
  17. Bartman

    Bartman SnowDog

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    I think I may give that a shot as I've changed out the o-ring which didn't seem to help much. Thanks for the tip.

    Bart
    #17
  18. YOGOI

    YOGOI Prick

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    The sprocket nut should be torqued to 100 Nm:deal . You need to bend the "sheet retainer" out of the way, torque the nut to 100Nm, and then bend the sheet retainer back down. The red dust is from the sprocket and the shaft wearing on each other becouse the sprocket nut is not tight.

    I'm sure no damage has accured to anything, but if left this way I would think somthing would suffer. Probably premature wear to the shaft seal.

    ...and who knows, maybe this has somthing to do with the clutch cylinder crack'n. Its all a pretty tight fit in there. A little extra friction, a little woble of the sprocker may make the chain contact the clutch slave, and after a while causing a crack. Who knows. Just keep an eye on your nut, and keep it tight.:1drink
    #18
  19. Speedzter

    Speedzter Been here awhile

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    Won't an Aluminum spacer/base plate conduct more heat into the slave cylinder, causing the O ring to harden even faster ?
    How about using a phenolic based material, or teflon ?
    I have been using Shell 10 weight fork oil in my clutch, after flushing all the old mineral oil out. The mineral oil that I flushed out was very black/dirty/contaminated. Still OK at 30k kms.
    Can't stop my clutch pushrod seal from leaking though !!
    #19
  20. gefr

    gefr Life is a trip

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    Thanx yogoi!!
    #20