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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, Bourbon. 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.
     
  9. Jetfixer

    Jetfixer Well-Known Member

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    Okay finally finished putting carbs back together only took me 3 months ( lol has been to cold to work in garage and was in no hurry either) these carbs were in poor condition , extra soaking on one carb the butterfly seal was totally goo , the butterfly plates were seized and the slides were froze took lots of PB blaster to free them up. The hats were rusted and I'm cheap so cleaned them up ,sprayed with self etching primer and painted with hammer rite silver
     

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  10. Ryengoth

    Ryengoth Active Member Premium Member

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    If you have the parts and pay attention to the shaft styles and orientation it really is not that bad. Just time consuming when things break during disassembly.
     
  11. Chitwood

    Chitwood Well-Known Member

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    I recently tried out the two #11 o rings for throttle shaft seals on my 83 750 midnight so I could get it on the road for cheap. Well, that completely backfired in my face. When I first put them together I had coated the orings in silicone grease and all worked smoothly. A month later and the throttle blades no longer operate properly. They open well enough but take about a minute to return to an almost idle position. My advice, buy the correct seals and do it once. I am so mad I have to pull those flipping carbs again. One because it's a pita, and two because I have it running so awesome.
     
  12. k-moe

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

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    You do have to work the throttle shafts quite a bit initally when using the o-rings in order for them to work properly.
    Maybe @Polock can chime in about that to clarify. I believe that he's had the same set of o-rings in this machine for several years.
     
  13. XJ550H

    XJ550H Well-Known Member Premium Member

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    he has advised me that using 2 #11 x rings works with out working the carbs

    just work them a little more you may not have to redo them
     
  14. Ryengoth

    Ryengoth Active Member Premium Member

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    Spray a quick shot of fluid film in the crack of the shaft where it meets the bore. then work them and repeat. the lanolin should last a bit longer until the rubber molds to the shaft.
     
  15. Polock

    Polock Well-Known Member

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    sorry to hear about that. here's the o-rings out of mine after, i don't remember how many years. the slides snap shut like a guillotine.
    the grease should be similar to this stuff, clear and a bit thicker than toothpaste. spray can silicone attacks the rubber.
    [​IMG]
    [​IMG]
    [​IMG]
     
  16. Jetfixer

    Jetfixer Well-Known Member

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    Could be wrong O ring material , Buna or vitron is they type.
     
  17. Ken Madden

    Ken Madden New Member

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    I'm having difficulty locating accelerator pump seals. I'm getting ready to do an overhaul to replace the shaft seals, Jets, floats, needle and seat, air fuel mixture screws. I have been unable to locate accelerator pump seals. As all have suggested, I would like to replace the rubber on these. Any ideas for a source.
     
  18. Polock

    Polock Well-Known Member

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    what kind of carbs are they? chances are they don't have accelerator pumps
     
  19. Ryengoth

    Ryengoth Active Member Premium Member

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    I think you may be thinking the choke piston is a fuel squirter?
     

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  20. k-moe

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

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    And the seals on the enrichment plungers (pictured above) are just dust seals.
     

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