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Won't idle.

Discussion in 'XJ Technical Chat' started by Paradox1559, Apr 30, 2019.

  1. Paradox1559

    Paradox1559 Member

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    I just got a 1981(82?) Xj650 (5N8).
    I would like to note that I am familiar with carbs, but I am no master.
    So, I can run on the enrichment circuit, but as soon as i turn it off the bike dies. Idling is not happening. I CAN use the enrichment and get moving, then turn it off down the road. It wont have much power, and it feels like it surges, but it'll run, and that's how I got it home. It looks like the carbs have been rebuilt, the gaskets seem new, and the Jets look suspiciously new. If someone has changed the Jets, I don't think they used the right ones. Any thoughts?

    View attachment 34702
     
  2. Toomanybikes

    Toomanybikes Well-Known Member

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    So maybe the so called “rebuild “ was not complete.
    “Church of clean” is an involved undertaking. Jets, gaskets, o rings, seals etc etc. Most bike shops will not do this because of the cost involved that many people won’t buck up to have it done.
    There are a few of us that do this work.
    Out west me , east is @hogfiddles.
    In most cases an idle adjustment and syncing is all that is required after you have checked the valve clearance.
     

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  3. Paradox1559

    Paradox1559 Member

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    I should still be able to get SOME idle. But I still got nothing. I'll be taking pictures tonight
     
  4. Timbox

    Timbox Well-Known Member

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    Pardox, we need a little back ground on the bike. Did the bike just come out of a storage shed, back of someones house, out in the back yard for yrs under some tree? Many of the folks that will help you out here will need to know how you cleaned or if you cleaned the carbs. The most common fact is, if they have not been cleaned as stated above, you will have issues. When the carbs are fully stripped down and cleaned as in the "Church of Clean" the bike will start and run well. Other issues could be some air leaks from cracks carb boots front or back.

    When you get a chance fill us in a little more and we will be able to help you out more.
     
  5. XJ550H

    XJ550H Well-Known Member Premium Member

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    first thing you should do is check valve clearances
    then warm up bike with enrichment circuit. then try adjusting the idle knob as you back off enrichment circuit. you should be able to set idle at 1050 or 1100 rpm.
    if you cannot adjust the idle with the knob it is indicative that your pilot jets circuit is dirty. that's the pilot jets and mixture screws.
    check your jet size numbers and check the air jets for proper location.
    jets.jpg
    are all the headers getting hot?
     
  6. Paradox1559

    Paradox1559 Member

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    The p.o. rebuilt the motor/carbs and added a 4-1 exhaust. The boots and seals all look new It was stored in a dry barn over the winter. I suspect he had no idea how to tune these....clearly neither do i
     
  7. k-moe

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

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    How long are you letting it warm up before shutting off the enrichment?
     
  8. Paradox1559

    Paradox1559 Member

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    Probably 3 min. At one point i drove it on the enrichment to see if it wasn't getting warm enough. No dice.
     
  9. Paradox1559

    Paradox1559 Member

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    So I just found the set screw by the enrichment plungers. None of them were even close to the same setting. I've put them at 2 1/2 turn, I will update soon.
     
  10. Paradox1559

    Paradox1559 Member

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  11. Paradox1559

    Paradox1559 Member

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    My jet sizes were;

    40
    110
     
  12. k-moe

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

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    Those are the idle mixture screws. 2 1/2 turns is a good baseline, but you will likely need to bump them closer to 2 3/4.
     
  13. Paradox1559

    Paradox1559 Member

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    Well, now it isn't starting at all...... I can get it to run on starting fluid, but it won't even put with the enrichment.
     
  14. Polock

    Polock Well-Known Member

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    did you set the floats at all? #1 and 4 look high so the wet set would be low. maybe it's just the picture
     
  15. Paradox1559

    Paradox1559 Member

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    I can't find definitive sources. What are these? Mikuni, or hitachi?
     
  16. k-moe

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

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    Can't find definitive sources?
    We must have missed pointing you to: The Information Overload Hour
    You have Hitachi carbs.
    Set the fuel levels wet: Setting the fuel levels

    Given the state of the idle mixture screws I would not trust that the PO knew anything at all about what he was doing.
    Assume that he did everything wrong.
    Just go through and double-check his work for now.
    IN THE CHURCH OF CLEAN

    You can sort-of test the throttle shaft seas for newness by removing the E clip from the outer two carbs, removing the plastic washer, and using a drop or three of automatic transmision fluid on them (one end at a time, set the carbs with the shaft end pointing up) and see if any of it leaks onto the throttle plate after a few minutes.
     
    Last edited: Apr 30, 2019
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  17. Paradox1559

    Paradox1559 Member

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    What are the butterfly shaft seals made of? I have the tools to make my own, I just need a material list.
     
  18. XJ550H

    XJ550H Well-Known Member Premium Member

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    you can use a couple of o rings I think it is #10 buna orings. there are a few threads on the use of orings
     
  19. k-moe

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

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    The good replacements have an X profile. Buna-N.
    They are inexpensive enough that making them isn't worth the wage you would pay yourself to do it.
     
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  20. Jetfixer

    Jetfixer Well-Known Member

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    Just an observation did you try turning idle adjustment screw in , if it is set to low then bike might only run with enrichment on. Idle should be 1095 to 1100 rpm is ideal.
     

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