My clutch slave cylinder modification

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

  1. BLUE(UK)

    BLUE(UK) Long timer

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    Maaaaaaaaaan.....i got an headache!!:cry :cry
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  2. union jack

    union jack Mis-Adventurer

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    Don't worry Red I've started taking the tablets again. No, what really pisses me off is KTM's general approach to fixing problems on what is generally a well sorted machine. Instead of going back to the drawing board and redesigning the thing properly (Like Evoluzione have) they keep flogging a dead horse so they don't have to issue a proper recall. Perhaps its the Bravian way to never admit your wrong.
    #22
  3. StevenD

    StevenD Hmmmm, dirt!

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    KTM does not 'MAKE' the unit, they just buy it of the shelf, the same many other manufacturers buy of.
    #23
  4. emelgee

    emelgee Been here awhile

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    You may well have something there - the volume of oil in the cylinder is very small and since it's pretty static there's nowhere for the heat to go.
    I got 20k miles out of the original unit on mine and just got the improved replacement from KTM - I couldn't really justify the cost of getting the Evoluzione version shipped to the UK. I'll change the fluid as part of my normal servicing routine and see how long this one lasts. If it goes for another 20k miles then I won't be too bothered if it needs changing again - it's not something I'l b fretting over.
    #24
  5. Kawidad

    Kawidad Long timer

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    Mine too.

    I'd say Woody is mentally on the right track about cause and effect, but I do think that the Evo unit is about as close to a "fix" as you can get. Ktm and others have been using the exact same hydralic clutch system on other bikes for years without issues, so it must be something specific to the 950s that cause the breakdown.
    #25
  6. ridewestKTM

    ridewestKTM Long timer

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    Best dialog in OC. A couple of additional thoughts. I am not there yet (mine's still working). But perhaps a silicone oil might be a good thing, or I don't know what the stuff is but the WP shock oil is incredible stuff.
    On the design: if the plastic is flexing perhaps an aluminum stiffener plate over the top? Hold it with longer screws and press around the center extrusion. Could be finned to help heat and offer a HNF. Another idea is make an extended pistion so it can't cock in the bore, take up the length with an additional spacer flange.

    just some ideas
    #26
  7. gefr

    gefr Life is a trip

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    #27
  8. RedRupert

    RedRupert Brit in the Soviet Union

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    I agree, but our circumstances are different. Maybe this why I have a more tolerant attitude. But you are right, because the bike is expensive and therefore should be good.

    I purchased my bike when it was 2 years old. KTM had extended the warranty from two to three years, which included me as a second owner. I thought this was a good gesture from KTM. They also agreed to supply and fit carb warmers for me, even though the bike was originally sold in Germany, where 2004 bikes were not fitted with carb warmers.

    When I purchased the bike, I was aware of the clutch slave cylinder and water pump problems because of OC, therefore I cannot get too pissed off when they go wrong.

    Judging by your (recent) high mileage, it sounds as if you use your bike to commute to work. If this is the case, I sympathise with you because failures can be a real pain if you HAVE to use your bike. I only use my bike when on holiday as it's too dangerous to ride where I live, therefor I have time to ponce around with the problems. But if I can't ride my bike when I'm on holiday I'll be absolutely furious!

    The problem with the clutch slave cylinder may lie with Magura. They make the whole hydraulic clutch system; so when KTM find that it fails too often they go back to Magura. Magura redesign it as (economically?) as possible and start shipping the 'redesigned' parts. I don't think KTM know THAT much about it. KTM seem to have dealt with the rear brake problem far better than they have the clutch problem. Is it because Brembo were more helpful, or is it because the brake problem is potentially dangerous?

    I didn't buy a KTM 950 ADV when they first came out because I didn't think they could build a RELIABLE completely new model with a new engine. It was better than I expected.
    #28
  9. RedRupert

    RedRupert Brit in the Soviet Union

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    Thanks gefr, I missed the photos that you posted on your thread - I must have been away when you posted them. I've read through that entire thread now, and can see that I agree with most of what you've said.

    However, I have not suffered from a cracked piston. I can't believe that the normal pressure from the clutch causes the piston to crack - it must be when the piston becomes jammed in the cylinder.
    #29
  10. RedRupert

    RedRupert Brit in the Soviet Union

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    Yes, I more or less agree. But why can't the fluid handle the heat? It's not THAT hot. I think the most important thing is to find a fluid that fits the bill. I'm convinced that the LHM Plus is the stuff - it's easy to buy in the parts of Europe that I know, but seems more difficult to get hold of in the USA. Citroen cars need this stuff, and I believe Rolls Royce and Bentley cars use it. Do they sell Citroens in the USA and Canada? Valvoline produce LHM Plus as well as many other international companies.

    LHM Plus a very high spec hydraulic fluid, and is thin.

    You can check the spec here:
    http://www.morrislubricants.co.uk/pr...v06c41q7p6=ELL

    It's what this guy is using:
    http://www.dirtbikerider.co.uk/websi...utch_oil/index<!-- / message --><!-- sig -->
    #30
  11. RedRupert

    RedRupert Brit in the Soviet Union

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    The main problem though, is the plastic spacer. When it gets hot, it distorts, and when it distorts, the piston skews and the system fails.

    I know it's all been said before, but for some reason the subject always gets off track

    So I think the permanent fix will be to replace the plastic spacer with an aluminium copy, and to use LHM Plus fluid. And don't forget, the plastic spacer is not the only heat insulator - there is more plastic behind the metal plate that the spacer sits against.

    Anyway, the above is what I'm going to try. I'll report back to OC when it fails :wink:
    #31
  12. gefr

    gefr Life is a trip

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    I believe the minor distortion of the plastic spacer causes the disalignment of the piston, while the high temperature causes the o-ring to soften. So the soft o-ring jamms the piston movement so the piston cracks.:cry
    #32
  13. evoluzione

    evoluzione Been here awhile

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    i've been away for a couple days and this is an interesting thread. but i thought i should point out that our slave cylinders come with a 10 year warranty. and we are setting up a distributor in the u.k. that can handles sales and warranty.

    now, as to the failure with this design. we found the main problem centered around the slip fit of the piston in the plastic spacer. this snug fit is required because the piston is too thin and will cock in the bore if it is not held properly. if the plastic spacer starts to distort, it will cock the piston and lead to failure. our design is self-supported so the piston can't cock sideways. we also use viton seals (which are the most expensive but also rated for the highest temperature).
    #33
  14. cpmodem

    cpmodem Orange Caveman

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    :deal
    #34
  15. ABYSS

    ABYSS KTM

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    SICK 'EM KEN
    #35
  16. RedRupert

    RedRupert Brit in the Soviet Union

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    Sorry. My mistake. :bow A 10 year warranty is a fine demonstration of your faith in your product.

    It's a pitty KTM don't do the same for the whole bike!
    #36
  17. RedRupert

    RedRupert Brit in the Soviet Union

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    Why go to the trouble of producing a complicated slave cylinder and a piston, and to source o-rings, bolts and bleed nipples etc, and to have someone anodize your product, when you can simply make a copy of the plastic spacer in aluminium?

    It does not make logical sense. But it does make business sense! Could you charge 180 US$ for a simple spacer - no. But you can charge that much for everything that Evo supply.

    The argument against making the spacer out of aluminium is that it'll transfer too much heat from the engine to the slave cylinder. But why does that matter? I think we can all agree that the engine heat damages the spacer, so if it was made of aluminium that would not happen.

    Then some say that the heat damages the piston o-ring. Mine looks and feels perfect, but if the heat does damage the o-ring, then why not use a viton o-ring?

    Then some say that heat causes the hydraulic fluid to fail. Well, there are suitable hydraulic fluids that will stand FAR higher temperatures than those of our hydraulic clutch, so why not switch to a better fluid?

    Many imply that the slave cylinder and fluid get too hot, but has anyone actually checked this? Is there proof? Does anyone know what temperature the fluid gets to? If no one can say, I'll check this myself in November when I'm reunited with my bike.
    #37
  18. gefr

    gefr Life is a trip

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    There could be an evo spacer though, with much less effort and design risk and much wider market. Everybody would buy one.
    Maybe you could give it a try.
    #38
  19. cpmodem

    cpmodem Orange Caveman

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    There's no need to denigrate Ken. He didn't come to us with some wild idea to make money off us. He was recruited by one of the Inmates to make a slave cylinder for our beloved Nine-Fiddy's. He graciously did just what he has done for many other bikes and made a masterfully designed piece of hardware that fixes the problem we asked him to fix.
    #39
  20. cpmodem

    cpmodem Orange Caveman

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    Did it sound like I said there was something wrong with "understand the problem and discuss its origins and the fixes."
    :deal
    I thought it was obvious that I was speaking to the false accusation that EVO was ignoring the problem because he couldn't make enough money off us by building the "correct" part (aluminum spacer). Nothing wrong with that, eh?
    #40