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Why you should replace butterfly (throttle shaft) seals.

Discussion in 'XJ Technical Chat' started by Jetfixer, May 12, 2019.

  1. Jetfixer

    Jetfixer Well-Known Member

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    So it is cold and raining off and on so no riding , I finally tore into a spare set of carbs I bought awhile back from Joe Elif . They were pretty gummed up and very dirty inside and out ... I like challenges :D I only wanted these a spare anyway. (Always like spares parts ) so got one carb tore down and soaking , when I pulled butterfly shaft out the seals were toast , I suspect at some point someone tried to soak carbs and this will tear up the seals . There is NO short cut breaking the carbs off the rack is only way ,and one other seals that is super critical is the fuel interconnect rail ....do your carbs right the FIRST time if it leaks fuel onto a hot engine well I dont think I need to explain. Anyway not sure about other carbs, when I rebuilt my carbs(on my seca ) seals did not look real bad but replaced anyway .
     

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  2. XJ550H

    XJ550H Well-Known Member Premium Member

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    no such thing as spare carbs, just carbs in waiting. now you have to find a bike for them its the right thing to do..

    replacing the seals is needed and you should not have to do it again for several years
     
    Last edited: May 12, 2019
  3. Ryengoth

    Ryengoth Active Member Premium Member

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    Mine had 18k miles and looked ok but they were not contacting the shafts at all.

    [​IMG]
    [​IMG]
     
  4. k-moe

    k-moe Pie, Bacon, Burbon. Moderator Premium Member

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    Exactly.
    Over time the plasticizers migrate into the atmosphere, causing the seals to shrink and embrittle.
    The process speeds up with exposure to ultraviolet light and/or heat.

    Stickied and edited the title for terminology.
     
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  5. Jetfixer

    Jetfixer Well-Known Member

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    So here are some pictures of the carbs before and after one is cleaned . The #4 carb float post was broke at some point , who ever did the repair did a good job drilled hole and put a pin in and JB weld . I have another set of carbs so will probably not use this body , but I might use it as is. 20190514_193254.jpg 20190514_193223.jpg 20190514_193254.jpg 20190514_193223.jpg 20190514_193254.jpg 20190514_193223.jpg
     
  6. Jetfixer

    Jetfixer Well-Known Member

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    So grabbed my other set of carbs , broke down the carb number 4 , got it soaking right now . Looking at this set of carbs there in better shape but were missing the diaphragms. The other set has diaphragms and complete.
     
  7. Nuch

    Nuch Well-Known Member

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    When I pulled my carbs apart, I found my throttle shaft seals to be petrified. They LOOKED ok, but they were hard as a rock. No chance they were doing the job they were supposed to be doing.
     
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  8. Jetfixer

    Jetfixer Well-Known Member

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    I'm hoping this thread will better show why you should take carbs to church . My second set I tore down today seals were soft and pliable look new , but I'm replacing them anyway.
     

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