950 carb refurbishing - pitfalls and experiences, please?

Discussion in 'Dakar champion (950/990)' started by Orange Toaster, Feb 28, 2013.

  1. Orange Toaster

    Orange Toaster Been here awhile

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    Hello good folks,

    I am considering giving my carbs an overhaul. Reason: The bike has done 65,000 km's and I am thinking it would need a bit of TLC, since the carb's have never been touched AFAIK.
    It also has developed a bit of "afterburning" in the one exhaust (some "popping" in the exhaust at idling). I honestly don't know if it is related to carb's but it could be...

    I am thinking taking the things apart and getting them cleaned with ultrasound. Also it might be relevant to replace certain parts.

    Now the questions:
    Apart from taking the carb's apart is there anything else I need to do before ultrasound cleaning?
    Also, for some bikes you can buy "carb repair kits", normally a set of new O-rings, jets, needle, etc. Does KTM supply this as a kit? And does anybody know a part number?

    Any other things I should know?

    Cheers
    OT
    #1
  2. MortimerSickle

    MortimerSickle Semi-Adventurer

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    Maybe they just need to be adjusted?

    I just had mine apart to rejet, and to move the needle clips, and the carbs looked perfectly clean inside. Everything seemed to be in good order at over 74000 km (early '04 model).
    #2
  3. Balsta

    Balsta Been here awhile

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    Just replace all little orings and gaskets BUT do also relace the vacuum diaphragm on each carburetor. I did and the response got fast clear and crisp. Old diphragms tends to stiffen with time which causes a slower pull-out by the vacuum slide.

    60031035000 VACUUM PISTON CPL.
    Two pieces required. Retail Sweden is SEK 635:-
    #3
  4. crazybrit

    crazybrit Long timer

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    I'm a little sceptical of the ultrasound cleaning. Sounds like overkill.

    I'd just lay out a towel, dissassemble, soak all metal parts overnight. Maybe replace pilots (as they are a pain to clean; plenty of places online sell jets cheap) and reasssemble. Possibly replace rubber components.

    The popping could be a slight air leak, have you checked the boots between the carb and the manifold.
    #4
  5. Orangecicle

    Orangecicle On a "Quest" Supporter

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    If I remember right, somewhere in Pyndon's thread he mentions that he replaced his carbs because of wear: http://advrider.com/forums/showthread.php?t=147440 If I remember right, Pyndon describes symptoms similar to yours, and he attributed it to air leaks around the shafts. 65K on carbs does not sound like a lot at all. But, it would be a good idea to clean them. I took mine apart at 25,000 miles, and the carbs had tons of tan residue in the bowls (dissolved Polyamide-6 from the tanks). Cleaned, reassembled, rejetted, and some FlexJet2s installed, and they are still running strong at 35K miles. :freaky
    #5
  6. Head2Wind

    Head2Wind MotorcycleMayhem

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    disassemble the carbs, clean all jets and passages thoroughly with spray carb cleaner, blow clear with compressed air, verify/set float heights and then reassemble.

    If anything needs to be replaced it would be the float needles.
    #6
    pbeezy and DistortedAxis like this.
  7. Katoom72

    Katoom72 Been here awhile

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    My rear cilinder does the same. Popping at idle only.
    #7
  8. DirtyADV

    DirtyADV Long timer

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    Glad to see a carb thread started.

    While ripping out the engine to look over the cylinder base gaskets I also plan to look over the carbs.

    It was not running as it should when starting to warm up the oil before removing engine studdering and not responding well to throttle.

    Found the edge of diaphragm cover for the front carb all sticky:

    <a href="http://www.flickr.com/photos/dirtyadv/8517367537/" title="KTM 950 carbs LC8 engine by DirtyADV, on Flickr"><img src="http://farm9.staticflickr.com/8531/8517367537_afb7830ce6_z.jpg" width="640" height="480" alt="KTM 950 carbs LC8 engine"></a>


    The rear was all dry. What could cause this? Oil from crank case breather?


    /Johan
    #8
  9. KtmPedro220

    KtmPedro220 Adventurer

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    As soon as a thread like this is started I wonder what I soubd do with mine. No issues as yet but always over cautious. Lol.
    #9
  10. RedRupert

    RedRupert Brit in the Soviet Union

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    #10
  11. DirtyADV

    DirtyADV Long timer

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    Had a leak there last spring so Im for sure looking at replacing them even if the leak sealed itself and lasted all summer:

    http://www.dirtyadv.com/season-of-2012-has-started/

    /Johan
    #11
  12. DirtyADV

    DirtyADV Long timer

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    Seems the o-rings for the inlets are on available in the gasket kit for the carbs:

    <table class="rgMasterTable" id="ctl00_ContentPlaceHolder1_rgPartList_ctl00" border="0" cellspacing="0"><tbody><tr class="rgAltRow" id="ctl00_ContentPlaceHolder1_rgPartList_ctl00__7"><td>
    </td><td>60031099000</td><td> GASKET SET KEIHIN 03
    </td></tr></tbody></table>


    And its not cheap since I guess you would need 2 kits? Anyone that can say what is included?

    Should it contain the diaphrams and be for both carbs price would be good!

    /Johan
    #12
  13. Katoom72

    Katoom72 Been here awhile

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    It's a gasket kit so my guess is the diaphrams are not included.

    [​IMG]
    #13
  14. GZERO

    GZERO Fixing stuff around

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    i think is a good idea, since the bike doesn't have that much kms, but it's been a long time since she left the factory.
    I would buy the gasket kit (only one needed), the diagphrams (2) (which KTM refers to as "vacuum piston") and a good carb cleaner and get to work.

    I've taken mine apart and my friends many times and i have good seetings, if you want shoot me a PM and i'll give you some tips and some setup points.
    #14
  15. Katoom72

    Katoom72 Been here awhile

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    Mind sharing those tips and setup points with us? :)
    #15
  16. geometrician

    geometrician let's keep going...

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    Throttle butterfly shafts wear and allow dirt & extra air into the intake tract.

    In the old days when you rebuilt Solex carbs (on aircooled Volkswagens) the shaft bore "gap" would really cause problems with idling & overheating from lean condition. When you ultrasonically or chemical-bath a carb body this area is washed clean of the accumulated dirt (& oils) that have helped seal the leak (somewhat) as it builds up over time. Upon installation the newly-opened passages will now leak more than before- which created numerous problems in performance (much to the amazement of the mechanic who washed & assembled everything properly, DAMHIK). The fix was to re-bush the magnesium-alloy carb body to fit the shaft again. The shafts were generally not worn. This was such a common problem that many VW shops re-bushed carb bodies on-site. A competent machine shop could do this if the have a ream long enough to cut both holes at the same time to make sure they are parallel.

    +1.

    On a the 90deg brass fuel inlet double o-rings I have found that if you have the carbs down & apart for a few days the o-rings will leak when you first start the bike. If you wait overnight the fuel re-swells the o-rings and they stop leaking again. This of course assumes you got all the hoses & cables happily routed in the airbox as you can put undo pressure on these fittings which the o-rings can't stop

    The oil on your front diaphragm is from the breather system. At 65k miles it's time for a leakdown test to see how much & where you are loosing your cylinder sealing- could just be a breather seal on the balancer shaft needs replacing. all in the HOW (thanks CpModem)
    #16
  17. DirtyADV

    DirtyADV Long timer

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    Sorry for stealing the thread Orange Toaster, dont think he had any trouble with any gunk in the carbs as I had.

    "Only" 55000kms on my engine.

    Dont want any more problems just lifted the cylinder cause of my Pyndon Syndrome.

    Maybe need to see if I can borrow a leak down tester to start with.

    /Johan
    #17
  18. GZERO

    GZERO Fixing stuff around

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    i wouldn't mind, but i need to know a few things about your bike:
    Mods
    Altitude and temps where you live.
    Type of riding
    Is fuel consumption important? or is power more important?
    #18
  19. Katoom72

    Katoom72 Been here awhile

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    Leo mufflers, SAS removed

    Sea level, -5celcius winter time 20celcius summer time

    Mixed dirt and tarmac, allot of accelerating hard. Don't care about top speed, rather have good bottom-end.

    Power, power and power!
    #19
  20. GZERO

    GZERO Fixing stuff around

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    Lets take it over PMs
    #20