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Sync screw?

Discussion in 'XJ Technical Chat' started by Xjrider92117, Feb 3, 2018.

  1. Xjrider92117

    Xjrider92117 Active Member

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    I have a bit of an idle problem with a 550 SECA. The valves are in spec and the carbs have been fully rebuilt. I have synced the carbs and adjusted the air/fuel mixture screws with a color tune.

    The bike acts as if there is a air leak (which I've checked for and I didn't find one) or the carbs out of sync (which I got very very close to perfect).

    When I press the sync screw down with little force the idle drops down to normal. So it seems there is something either binding or sticking some how.

    My throttle response is good and snaps right back when I grab a handful. The cable isn't binding.

    I have a new stock paper air filter. I also have new manifolds engine to carb and carb to airbox.

    The only thing I can think is to pull the carbs and recheck the return springs. I guess I could have installed wrong.

    Any thoughts before I pull the carbs??

    Thanks
     
  2. Polock

    Polock Well-Known Member

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    don't know about mikuni but hitachi needs to be lined up when you reassemble the rack for things to work smoothly. after it's all together i loosen the rails a little and snap the throttle a few times to let the carbs find their happy place on the rails then snug the screws and snap a few more times to make sure then tighten the rail screws
     
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  3. Xjrider92117

    Xjrider92117 Active Member

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    I use a level on all sides to make sure everything lines up.

    But...

    I'm gonna pull them and loosen the rails.
     
  4. XJ550H

    XJ550H Well-Known Member Premium Member

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    the deck of a table saw works well for carb reassembly thick piece of tempered glass works too. chacal rents a plate by the day
    HCP20990 Aftermarket carb rack re-assembly ALIGNMENT PLATE.

    are the butterflies properly reinstalled not binding or rubbing the carb throat? centered well?


    gaskets on the carb boots?
     
    Last edited: Feb 3, 2018
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  5. Xjrider92117

    Xjrider92117 Active Member

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    Yeah, for the butterflies I use the same method as mentioned above by polock.

    New gaskets from chacal.

    I pulled the carbs and did as polock suggested. Went for a nice 20 min ride (it's 70 degrees right now). Up and down the freeway. On my way home hit a few lights. Idle dropped like it should. Seems a lot better now, but not perfect. I'll do another sync tomorrow and see how it goes.

    Thanks for the suggestions!
     
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  6. Nuch

    Nuch Well-Known Member

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    Why make us jealous? That's just cruel.
     
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  7. Xjrider92117

    Xjrider92117 Active Member

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    :D
     
  8. Nuch

    Nuch Well-Known Member

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    I'll get there one day. I have friends in Manhattan Beach. I'm determined to do it on 2 wheels.
     
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  9. Xjrider92117

    Xjrider92117 Active Member

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    And I hope you share the story!
     
  10. Xjrider92117

    Xjrider92117 Active Member

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    For forgot to mention that I also used some "cable life" on my throttle cable. That may have helped some.
     
  11. k-moe

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

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    If you still need to isolate the problem, unhook the throttle cable and manipulate the thottl linkage by hand (in neutral, on the center stand). That will telll you if it's the carb alignment, or the cable/ throttle tube. You might want to just go ahead and pull the throttle tube off for a good cleaning, and re-lube it with graphite.
     
  12. Polock

    Polock Well-Known Member

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    sometimes that can work wonders
     
  13. Xjrider92117

    Xjrider92117 Active Member

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    I actually had a new throttle tube and replaced the old one which had a throttle lock (cruise control) on it. I clean but didn't grease it. I will do so.
     
  14. k-moe

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

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    Do not use grease! Use a dry graphite powder. Grease will slow the action of the throttle tube, and gum-up in colder temperatures. Grease also gets gooey as it drys out, and as dirt works into it, which can lead to throttle return problems.
     
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  15. Xjrider92117

    Xjrider92117 Active Member

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    Sorry. That's what I meant
     
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  16. Xjrider92117

    Xjrider92117 Active Member

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    Didn't get as much done today as I wanted but... I dusted the throttle tube with the graphite. Adjusted the throttle a bit. New plugs and caps. Adjusted the back brake a little. I really wanted to try to sync it again but didn't have time. Still got to ride today so that's always good. I'll get back probably next weekend with an update.
     
  17. Stumplifter

    Stumplifter Well-Known Member

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    Synching the carbs, having them truly dialed in tight, can really make a surprising difference. It did for me.
     
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  18. Xjrider92117

    Xjrider92117 Active Member

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    I got to sync the carbs this weekend. It made a difference. Still not perfect but a bit better.

    I still need to tune with Colortune and sync again.

    Something else weird is going on. If I go out to start the bike cold it fires right up. If I ride for an hour and turn the bike off it fires right back up. If I want 5 minutes after a ride it struggles to start. Could this be caused by rich or lean conditions?
     
  19. Polock

    Polock Well-Known Member

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    cold engines like richer, hot ones like leaner. after 5 minutes your is neither. if the carbs are tuned right and this happens you might need to learn just the right throttle routine to make it go. my lawn mower always did that
     
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  20. XJ550H

    XJ550H Well-Known Member Premium Member

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    turn petcock to prime for 5 seconds then try in the 5 min start
     
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