My clutch slave cylinder modification

Discussion in 'Crazy-Awesome almost Dakar racers (950/990cc)' started by RedRupert, Oct 17, 2007.

  1. adiablolex

    adiablolex Lost again

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    Sorry to bring this back up but I was trying to prove a point back on post#17 about shit getting into the spacer and slave and destroying everything plus fluid getting too hot and eventually braking down.

    These are some pics I took after another 5,000 kms of abusive behavior, including some mild:evil watercrossings.
    KTM SLAVE001.jpg

    notice the very distict line of clean surface surounded with dirt.
    The grease I used this time is high pressure high temp. The two blobs of blue in the middle are the "packing" material I've used on the other side of the spacer, which should act as a heat sink.
    Anybody ideas??
    #81
  2. adiablolex

    adiablolex Lost again

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    KTM SLAVE002.jpg

    the cavities on the spacer are the two blobs from last post. Some of the sand in there, fell inside while I was removing it. I usually wash my girl before operating like that.:bubba
    #82
  3. adiablolex

    adiablolex Lost again

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    KTM SLAVE003.jpg

    this one again shows the cleanliness between the two pieces. As you can see my spacer was already slightly distorted before I did this.
    #83
  4. adiablolex

    adiablolex Lost again

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    KTM SLAVE004.jpg

    this one shows the rubber spacer on the pushrod, nice and tight like back in highschool:evil
    #84
  5. adiablolex

    adiablolex Lost again

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    KTM SLAVE005.jpg

    another view of the rubber sleeve, courtesy of KTM emission crap.
    #85
  6. adiablolex

    adiablolex Lost again

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    KTM SLAVE006.jpg

    and another one of the sleeve, it fits tight on the pushrod, but has a bit of play on the piston side, notice how I cut it a little shorter than the length so it doesn't interfere with that ball bearing.
    #86
  7. adiablolex

    adiablolex Lost again

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    KTM SLAVE007.jpg

    this one here shows the heat sink grease pack between the two, also notice that I didn't bleed all of the old crap out of the slave, so this time I did it properly. (where's my new master cylinder CJ?)
    Tell me what you guys think, if the Evo unit is using the same spacer wouldn't this crap still get under there and eventually eat the seals up?
    Apologize for bringing a dead horse back :asshat

    Cheers
    Alex out
    #87
  8. adiablolex

    adiablolex Lost again

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    Since everybody in this thread has determined that the failed fluid is the major curlpit here why don't we just get in line for the only thing that will cure the source of the problem?

    http://www.advrider.com/forums/showthread.php?t=280067 :norton

    Need to give credit where it's due, that's for sure.
    #88
  9. gefr

    gefr Life is a trip

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    Because of extreme heat and torsion forces. This leads to piston disalignment and fluid leakage or o-ring jamming.
    Piston disalignment produces friction which produce debris that turn the liquid black. My understanding of things.:huh
    #89
  10. adiablolex

    adiablolex Lost again

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    The spacer distortion is definately to blame too, I'm just not buying the fact that it breaks the fluid down, this is more of a heat transfer/poor fluid heat retention which can easily be addresed by increasing fluid volume(see last post). Again Gefr, I appreciate all the research you've done on this part along with everybody elses, I would just like to draw my own conclusions.
    Evo is on the right track by producing this excelent slave design, yet I don't think it completely fixes the problem.

    Say hi to Motherland for me
    yasou
    Alex
    #90
  11. adiablolex

    adiablolex Lost again

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    Wow, it looks even better off the bike.
    How about getting one for the bike and one for the living room in a glass display.:bow
    #91
  12. evoluzione

    evoluzione Been here awhile

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    just curious - has anyone actually measured the fluid temperature at the master cylinder? i can see the fluid getting warm at the slave cylinder but the clutch line will act as a "radiator" and i would expect the temperatures to drop dramatically by the time the fluid reaches the master cylinder.

    conversely, if you cool the fluid at the master cylinder, what "mechanism" forces this "cooler" fluid all the way into the slave cylinder? even when you are trying to flush the fluid from the system it requires removing and disassembling the slave cylinder to get that fluid out.

    just looking for actual info, not guesses.
    #92
  13. ABYSS

    ABYSS KTM

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    I am not sure I understand.

    While I would like to have the larger reservoir I cannot see where this will help with the heat all that much. The system is not a loop so there is no way for the cool fluid to force the hotter stuff up.

    We all understand heat rises and cold drops but if they are in the same path the heat is just going to warm up the cool fluid and loose the effect.

    In the clutch setup there really isn’t going to be all that much heat rise. My Master cylinder after several hours of hard clutch work is just as cool as ever.


    I think if a proper cooler was to be designed it would have to be a close loop system where fluid is being cycled threw the slave therefore allowing it to cool before returning.

    Anoher way you could keep the slave fluid cool would be to cross drill the spacer and install threw tubes for airflow on the back/inside of the cylinder. It is tremendously effective and durable and has been done before just not on bikes.
    #93
  14. adiablolex

    adiablolex Lost again

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    I can see how measuring the master cylinder temperature will aid in diagnosing the problem at hand, yet the fact is that the fluid is breaking down prematurely because of heat/poor dissipation/wrong type for the application.
    The line itself would be able to act as a radiator if it were of a larger diameter, which is not the case.
    As far as the mechanism forcing the fluid to the slave, I'm under the impression that everytime the clutch is used it pushes the fluid down the line to the slave and when released it pulls fluid back up. Now the mixing is really miniscule because of the line diameter, yet enough to contaminate the master cyl fluid as proven by all of us having to change the fluid on the master on a regular basis.

    You're definately on the right track by producing a slave that's far superior to the stocker, yet I think it's not the total cure.

    Let us know what you think.
    Alex
    #94
  15. Pahkis

    Pahkis n00b

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    Hi all,

    i have 35000 km driven LC8 and i had a clutch failure.
    The reason for this was a cracked piston in the slave cylinder. The fracture is on the oil side of the piston so it tells me that the heat nor the piston alignment (copper/bronze ring inside plastic) sticking is not the cause.

    I believe that the connecting rod bearing ball inside the piston is badly designed. It is simply too deep and too close to the spring adjuster so the material thickness gets all too small.

    here is some photos of the fracture in the pistons spring aligner and the leak cause


    Regards, Pahkis

    Attached Files:

    #95
  16. gefr

    gefr Life is a trip

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    Having the slave cyl failing on me 5 times and presently at 80k kms I replaced my slave cyl with my copy of the piston and the spacer. The piston is made of hard bronze used for flange production (with thicker bottom at the ball nest) and the alluminum is a "good" alloy. Nothing more I could add. In my copy, all different diameters in the piston drive on the spacer are reproduced. The replacement was done last November while temperatures were not too high (in the viscinity of 10C). The piston developed a minor crack that was invisible. Only pressing water with my finger from the side of the bearing ball showed there was a crack there.
    Very early to celebrate but
    I believe I am having very good possibilities to have the problem tackled.
    I want to emphasise I have no scored cylinder.
    I should also report my clutch fluid was black because of solid particles that point out to wear at the master cylinder. I wonder what the seals look like. I am convinced the fluid at the master cyl does not get black because of temperature at the slave cyl.
    Filled with mixed fork oil of viscosity 10 and 0. Viscosity 10 is too dense. Cheers.
    #96
  17. gefr

    gefr Life is a trip

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    Hi there from motherland.
    The evo unit does not rely its alignment on the plastic spacer shape, so is solving the problem altogether, eventhough it uses the OEM plastic spacer.
    I also noticed some wrenchers here reporting the use of hydraulic clutches succesfully in other dirt bikes. I think the major factors that push these components beyond their limits are eccessive heat from a strong and very compact engine and powerfull clutch springs because of the strong and torqey engine. So the beautiful compact design of the engine is also its weak point. Cheers.

    P.S. Yes sir,the pistons crack because of oil pressure in the system and aluminum fatigue. Not that strange. I sure had them fail more often when riding with a pillion in heavy traffic in the summer.
    #97