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XJ550 Carb Problem, Please help!

Discussion in 'XJ Technical Chat' started by Deathalo, Jun 7, 2010.

  1. Deathalo

    Deathalo Member

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    So, I just bought an 82' XJ550 and I decided I'd clean and sync the carbs. The guy who sold it to me said he rebuilt the carbs but they needed to be synced. So I opened em up, following the guides posted on here, and cleaned em off good. They weren't very dirty or gummed up, so the job was fairly easy, but after I put them back together and got ready to sync them, I ran into a snag.

    My idle adjustment screw doesn't seem to be pushing the throttle at all and therefore the carbs are staying completely shut unless the throttle is pulled by me. This would probably explain why I need to put the choke on halfway to get it to idle. Anyway, the screw seems to be just missing the tab it should be pushing.

    I don't know if this is a result of wear or from the carb rebuild, but I'm pretty sure they are mukuni carbs. Here are some shots of what I'm dealing with.

    These are the carbs without the idle adjustment screw attached.
    [​IMG]

    This is the idle adjustment screw.
    [​IMG]

    Here are the carbs with the screw attached. Note how the screw is just to the left and below the tab, just missing it.
    [​IMG]

    [​IMG]

    Anyone have any ideas on what to do? I was thinking maybe the tab should be bent down more? If it were it would hit the screw dead on... I just don't know how to bend it without snapping something off. I checked to see if the the screw was bent, but it seems straight enough. I'm not sure if there's a piece missing or not, I'm sure a secured bolt on the end of the screw would be effective to push the throttle tab... please help me out, I'm new to this and kinda out of ideas at this point, unless I just didn't hook it back up properly?

    Thanks.

    -DH
     
  2. wizard

    wizard Active Member

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    are you sure they are the right carbs for the bike? I've looked at the parts diagram for '81 '82 & '83, none of them show that quadrant, it's normally a lever with a flange turned at 90 deg, don't try to bend anything until we get a 2nd opinion.
     
  3. Deathalo

    Deathalo Member

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    I'm pretty sure, they seem identical in every other way to the other carbs people have posted in cleanings and syncs. And the bike ran fine other than the idle. That tab almost looks like it should be bent at 90 degrees, so I'm thinking maybe it's some weird fluke where it just wasn't bent all the way during manufacturing? I don't see why every other part would be just like other carbs except for this tab, even the idle adjustment screw is the same. Thanks for the response though, I'll wait for more opinions before I proceed.
     
  4. bigfitz52

    bigfitz52 Well-Known Member Premium Member

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    OK: I've got two 550s and two spare racks of Mikunis, so this isn't an "opinion" I just went and looked.

    That tab is supposed to be at 90* to the quadrant.

    Wiz, he has all of the correct parts;

    Somehow that tab has already become bent away from its original position. My concern would be that it will snap off when bent back.

    On all 4 of my examples, that tab is at a perfectly square 90 to the quadrant, and the screw pushes on the edge of it. Like I said, I would be very concerned that bending it BACK will break it off or weaken it to the point it will fail in service; I would say go ahead and bend it toward 90* just enough for the idle screw to engage the edge of it sufficiently then stop.
     
  5. Swissjon

    Swissjon Member

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    By the looks of things, someone has already bent that because they ran into this issue before. Bending it towards 90 degrees looks as though it will move it away from the screw.

    I wonder if you aren't missing a spacer or have a spacer on the wrong side of something??
     
  6. Deathalo

    Deathalo Member

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    Thanks bigfitz, I think you're spot on, it definitely looks like it should be at 90 and it just got bent back. I appreciate your help in the matter, do you think I should try and heat up the metal first or just slowly cold bend it?
     
  7. parts

    parts Member

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    If you have the option of heat then do it.
    If all else fails you might be able to use a couple nuts and a
    washer on the screw end. It might provide a wide enough
    flange to make contact with the throttle plate.
     
  8. Deathalo

    Deathalo Member

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    Yeah, I was toying with the idea of a nut locked on the end, I'm sure that would be enough to push the throttle. I'll try bending it carefully first, if it doesn't want to budge or if I get the feeling it's going to break, I'll just get some nuts.
     
  9. chacal

    chacal Moderator Moderator Supporting Vendor Premium Member

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    There is supposed to be a 6mm thick (1/4") aluminum "spacer" (washer) that fits between the quadrant and the throttle shaft rubber seal.....perhaps it is missing?
     
  10. RickCoMatic

    RickCoMatic Well-Known Member

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    The Idle Adjustment Rod is missing the Linkage because the "Shelf" that the Rod is supposed to hit has been pried to a nearly perpendicular angle from its 90-Degree angle that would allow the Rod to have contact.

    Open the Throttles by the Wire Pull.
    Withdraw the Rod a few turns leaving the END of the Rod exposed.

    ATTACH a Tight-Fitting Nylon Bushing to the End of the Rod.
    "Force-thread" the Nylon Bush on the Rod.

    The Outside Diameter of the Bushing will contact the Linkage and move it.

    Bending the Shelf on the Linkage is liable to snap it off.
     
  11. Deathalo

    Deathalo Member

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    Yeah, that thing's not budging and I'm too afraid of snapping it to put any more excessive force on it. So, I'll take your advice and go to the local hardware store and find a tight fitting lock nut or bushing.
     
  12. wizard

    wizard Active Member

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    I would bend the tab back to where it should be & have it brazed / welded, any other 'fix' will come back and bite you in the a...
     
  13. bigfitz52

    bigfitz52 Well-Known Member Premium Member

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    I tend to agree. Bend it back; if it breaks off then either get it brazed back together or replace it.

    TIP: Don't use pliers. Use a small adjustable wrench, and close the jaws fully on the tab. The flat, even, complete parallel support will prevent any twisting or uneven force that might contribute to breakage.

    Bend slowly and in one even motion. Stop short, it won't need to go to completely 90* to be fully functional.
     
  14. RangerG

    RangerG Member

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  15. RangerG

    RangerG Member

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    Double post
     
  16. Deathalo

    Deathalo Member

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    Well, I went to the hardware store and got a nylon bushing which fit just fine on the idle adjustment screw and was able to push the throttle lever as seen here:

    [​IMG]

    But then, I read the most recent posts and decided to give bending another try using the tips bigfitz suggested with great success:

    [​IMG]

    As you can see from the picture above, I was able to bend the tab down enough to get the screw to push the throttle lever securely to the desired position. I'm glad I was able to bend it, the nylon worked well but this seems like a more durable solution as long as it doesn't bend back (although I don't see why it would).

    Anyways I wanted to thank all of you for your help with this, you all were very knowledgeable and gave great advice! Thanks again!

    -DH
     
  17. bigfitz52

    bigfitz52 Well-Known Member Premium Member

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    It won't bend back. If YOU didn't bend it (and we do believe you, honest) then a numbnuts PO or some goofball he paid bent it for gawd only knows what perverted reason.

    As long as the lever is acting on it securely through its very small necessary travel (fine-adjusting the idle) YA DONE GOOD.

    Blame the PO.
     
  18. RickCoMatic

    RickCoMatic Well-Known Member

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    You had the problem licked when you had the Bushing on there.

    Now, the bent-over piece MAY interfere with the travel of the Linkage as you adjust that Sync Screw.
     
  19. Deathalo

    Deathalo Member

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    I don't think it will interfere, as it's bent in more of the RIGHT direction rather than the WRONG direction. I tested moving the throttle and it seems secure and fluid now. The only reason I removed the bushing and bent it was because the nylon could get bent back with too much wear or possibly crack under stress and heat. This seems like a much safer bet, but I still have more bushings just in case :p. And of course, I appreciate everyone's ideas, if the tab didn't bend back as easily as it did with the other techniques, then the nylon would've been my best option.
     
  20. Swissjon

    Swissjon Member

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    It works, well done. No point in touching it now and risking metal fatigue. No stop fiddling and go ride your bike :)
     
  21. Deathalo

    Deathalo Member

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    Quick question, when reinstalling the carbs on the bike, should I Prime them before starting up the bike? If so, for how long do I leave it on Pri.
     
  22. seaguy

    seaguy Member

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    10 seconds should be long enough for each to get enough for starting. You would be suprised at how long that bike will run with the supply shut off.
     

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