Ugh! Clutch master/slave is gone! HELP!!

Discussion in 'Dakar champion (950/990)' started by Farscape, Sep 25, 2012.

  1. Farscape

    Farscape I'm eat up with this shit, it's a disease...

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    731
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    Okay, I thought I had this fixed, but it failed again the same way...

    Symptoms: Clutch lever pulls all the way back to the bar with no resistance and no disengagement of the clutch.

    First fix: Not noticing any leaking from the slave cylinder, I "thought" it was okay and focused on the master cylinder. I replaced the master cylinder piston with the kit from KTM. This seemed to fix it as the clutch returned to normal operation and I even rode it for a while with perfect results.

    Next failure: I rode to work today, seemed to work fine until I went out to lunch and it failed the same way again. I rode it home with no clutch.

    So, what the hell is wrong? The piston replacement didn't fix it. Is it still the master cylinder? Maybe the bore is wallered out? Is it the slave somehow?

    Notes: I got a good bleed and used Mobil 1 full synthetic trans fluid.

    Let me know what you think...
    #1
  2. spencergt66

    spencergt66 Been here awhile

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    Take the stock slave cyl and throw it away get a billet one the have 2-3 piston seals no more issues I had mine do the same also if you are rebuilding yours make sure you use a viaton o-ring
    #2
  3. AdvGa

    AdvGa Long timer

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    #3
  4. slackmeyer

    slackmeyer Don't mean sheeit. .

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    take off the slave cylinder, and see if there's any fluid leaking from the back. I've replaced the O-ring a couple times, but stock slave is still going strong after 60k. Mcmaster Carr sells the good o-rings.
    If it's not the slave, probably time to start looking for a new master, they're not always rebuildable.
    #4
  5. azcagiva

    azcagiva new orange flavor

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    -021 o ring
    #5
  6. knobie

    knobie Adventurer

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    Does the clutch feel exactly the same with the bike cooled off? If the clutch works when engine is cold then it is due to boiling the mineral oil in the clutch system. I've had that happened to me on a different KTM with a Magura clutch which use mineral oil vs. break fluid on Brembo clutches. The mineral oil has a lower boiling point.
    It is far fetched but if that's the case your engine may be overheating. Mine did it because of engine oil level too high...adjusted the oil level and clutch worked fine.
    Also, if the mineral oil level in the clutch reservoir does not go down then it is an indicator that the slave cylinder seals are fine. If those are bad you lose oil.
    #6
  7. TheMuffinMan

    TheMuffinMan Forest Ranger Magnet

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    Could be an air bubble made its way into the slave, it's incredibly hard to bleed the bubble out of the slave in that case. Has caused me many frustrations until I figured out what's going on. The new design 2008+ OEM slaves average 40,000 miles or so I've heard. Longer if you flush the fluid every couple months to get the grit that develops out.

    I'd try taking the slave off, filling it with fluid first, then attaching the line and bleeding the system. If you still have trouble I'd say your master is toast. It's well documented that the master rebuild kits don't work since the culprit is scoring of the barrel. If my master ever goes out I'm going to find an aftermarket replacement, but until it does I'm not going to worry about it.

    And yeah if your fluid level is dropping you have a leak, if it's not then you don't and the seals on the slave are fine.
    #7
  8. erappaport

    erappaport pray for rain

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    Got the McMaster number for these? I'm running an evo now, but would like to rebuild my stocker for a spare. Probably shoulda tried that first, but money seemed less scarce at the time. Maybe a lesson there.. :1drink

    Thanks either way.
    #8
  9. geometrician

    geometrician let's keep going...

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    I'm sure you don't want to keep throwing money at a problem... however may I suggest you switch to an Oberon clutch slave... as for seals it has a lipped seal that uses the hydraulic pressure to press the seal into place- no o-rings (like KTM & Evoluzione) to replace or leak.

    I got mine off eBay and haven't had a single problem since, from the installation to the bleeding to every day hard use. Didn't spring for the fancy aluminum backing piece which they say acts as a heat sink. Personally I think it would only transfer engine case heat to the slave & bring it up to the engine temp, so to heck with that...

    The GREAT thing about this design is any air in the slave cylinder goes to the highest point- which is right where Oberon put the bleeder screw, which is part of the banjo bolt- that means you bleed the cylinder as well as any air caught in the lines' banjo fitting. Further, with this design you leave the unit in place while bleeding, so you don't have to mess about with a 3rd hand or keep the stock piston from coming out while pumping new fluid in. This is how they all should be from the factory

    I use 2.5wt suspension fluid (fork oil) and prefer it to the mineral oil, including Magura's Blood... has a higher boiling point and (being suspension fluid) keeps air out.
    #9
  10. dad2bike

    dad2bike Retired! Cranky Old Fart Supporter

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    What he said.
    Size -021 O-Ring Viton would be best. You can get the o-rings many places.
    I've learned to carry a couple of them on my bikes as well as a small pair of snap ring pliers to get the slave piston out. Of course a small bottle of mineral oil as well in my spare kit.
    #10
  11. omnivore

    omnivore SuperSportTourer

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    Oberon. I got mine on EBAY....amusingly enough.
    I did an EBAY search and the cheapest one on EBAY was at Blue Streak Racing. This is a shop less than an hr from me, that sponsors my racing efforts for the last 2 summers. I never considered calling them when my KTM had issues, but sure as shit they had a nice orange one is stock. Shipped t my door was less than $140 CDN
    #11
  12. Farscape

    Farscape I'm eat up with this shit, it's a disease...

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    No clutch, COLD or HOT. Thanks for the idea though...

    The slave isn't leaking... It's looking more and more like I need a new master cylinder. Crap :huh
    #12
  13. AdvGa

    AdvGa Long timer

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    Sorry it is not working for your, here is a link to some other Magura Options:

    http://www.advrider.com/forums/showthread.php?t=756603&highlight=magura+master&page=3

    I believe the ADV has a Magura 8mm type while others are substituting the 9mm, 9.5mm and 10.5 mm units.

    One of the reasons I went with the 16mm Accossatto unit is that it is a Radial unit and has a Visible Reservoir and carries about 3x the fluid level.

    The only loss to me was I had to get another type of Mirror unit since the above one does not have an attachment for one... which is really better.
    #13
  14. slackmeyer

    slackmeyer Don't mean sheeit. .

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    I think it's 10.5 stock, actually. It's written on the underside of the lever perch, I just saw it the other day.
    #14
  15. AdvGa

    AdvGa Long timer

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    Thanks for the clarification... I knew it was somewhat smaller than the 16mm I installed.
    #15
  16. mamacone

    mamacone Been here awhile

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    The 9.0 is a good upgrade, really makes the pull easy. Couple of things to keep in mind is the 9.0 will not work with the stock horn, blinker and light switch combo. You need to change to a smaller switch assembly, the 9.0 does not have enough clearance. I bought one from highway dirt bikes, when it arrived it was a Tusk product (rocky mountain atv). Sicass racing sells one as well. You can use the same mirror by swapping a couple pieces from the stock master cylinder. I choose to go with a different mirror that is separate from the master cylinder. In the end was a great mod and cost about 1/2 the price as the KTM oem master cylinder. The wiring was not to bad, a little soldering and identify wires and couple of hours later finished.
    #16
  17. Head2Wind

    Head2Wind MotorcycleMayhem

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    Oberon is pretty much the only solution that I know of for replacing the slave with a aftermarket slave cylinder since Evoluzione is no longer in business. I also run (and like it alot) either 2.5w or 5w Redline suspension fluid based upon how crisp I want the return of the lever to be. IMO, 10w is too thick and makes the clutch to sluggish on quick changes.
    #17
  18. Uller

    Uller Done with this BS

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    There is also Sigutech out of Germany. KTM Twins sells their products in the US. It is a little cheaper however, to purchase directly from the Sigutech site using Google Translate (it is a German Website). Quick shipping.

    Their unit is a (3) o-ring configuration. They also sell an uprated plunger for the stock slave housing which has (2) o-rings instead of one.

    http://sigutech.com
    #18
  19. gefr

    gefr Life is a trip

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    http://advrider.com/forums/showpost.php?p=18475532&postcount=51
    #19
  20. Farscape

    Farscape I'm eat up with this shit, it's a disease...

    Joined:
    Aug 20, 2005
    Oddometer:
    731
    Location:
    Edmond, OK
    How successful do you think I would be in cutting off the mounting clamp portions of my original KTM clutch master cylinder and a new Magura 10.5 master cylinder and having someone weld the KTM clamp onto the Magura 10.5 master cylinder?

    What kind of material are they? Do you think the heat will distort the bore?

    I'm just thinking out loud here... My next idea is to make a spacer for the mounting portion of the Magura 10.5 to get it to clear the switch pod.

    Any ideas are welcome.
    #20