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white ceramics need help

Discussion in 'XJ Technical Chat' started by mfchapman, Sep 10, 2008.

  1. mfchapman

    mfchapman Member

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    Hey all,

    my pilot mixture screws are 3 turns out each. The bike (85 xj700 maxim) idles good at these settings but all plugs look very clean at idle, no color on the ceramics at all. How far out will these things turn? If they are all the way out I should be fouling at idle right? Should I turn the screws to 3 1/2 and run for 1 minute then check that plug? If turning these has no effect but it still idles and runs great could it still be a clogged enrichment circuit? This bike is my commuter and I don't want to burn a hole in the pistons (obviously).


    Thanks in advance
     
  2. bill

    bill Active Member

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    3 turns is a starting point. turn the screws out a couple of degrees, small changes are best. Run the bike at 4 or 5k RPM for 15 sec or so (be sure to have fans on it to keep cool) and hit the kill switch without returning to idle. Check the plugs. Keep adjusting in small increments, it does not take much, until you get the nice tan color. This will get you real close.

    Then search plug chops on this forum to see how to do the full load wide open throttle tweaking.
     
  3. mfchapman

    mfchapman Member

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    ok, I'll try that. I have been checking after about 30 seconds of 1k idle to little avail. One plug blackish but maybe from revving?


    Thankx very much
     
  4. bill

    bill Active Member

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    Idle won't get you the color you are looking for. Reving shouldn't get you black. When you have the correct color there may be some small amount of black on the thread part but it is the insulator you are worried most about.

    Search on plug read and you will see posted pictures with folks requesting opinions on color. Will give you a good idea of what you are looking for.
     
  5. mfchapman

    mfchapman Member

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    I've tried chopping at just about every rpm and white, white, white. There was one time when I saw a decent amount of brown but I can't reproduce the results. My plugs are clean and the bike is idling and running great with all four mixture screws out 4 1/2 turns. Why does pilot mixture effect plug color at high speeds?


    Sincerely frustrated.

    P.s. Does chacal sell mixture screws, I've got one that is pretty hard to turn, possible bent the wings and they are pressing against the thread walls.
     
  6. bill

    bill Active Member

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    Yes Chacal has all the parts - screw, spring o ring and washer.

    4 1/2 is way out. I can think of 3 possibilities, The Idle circuit of your carbs is plugged, you have air leaks or your jet is the wrong size.

    To check for air leaks probe with a propane torch (unlit of course). the engine will rev if the propane is drawn in by a leak.


    To answer your question here is a post by Rickcomatic I hope he doesn't mind my reposting:

     
  7. mfchapman

    mfchapman Member

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    What is the idle circuit comprised of? Is it the pilot jets or further into the carb? I have not found any air leaks. Whoever owned the bike before me had ngk bp7es spark plugs in the bike instead of the recommended 8's. If this is not an error on his part, could it be an indicator that he changed the jets? Seems like he should have gone cooler with the plugs if that was the case. To my knowledge, everything is stock so I guess I need to know where to clean.

    Thanks for your help Bill.
     
  8. mfchapman

    mfchapman Member

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    Is is likely that all four carbs would be clogged?
     
  9. RickCoMatic

    RickCoMatic Well-Known Member

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    Anything's possible when dealing with PO's!

    I have seen Carbs come in here with:
    The Wrong Jets
    Mixed Jets.
    NO Jets. (Found them loose in the Flost Bowl)
    Drilled-out Jets..
    Clogged beyond belief Jets!

    If you uare that far out with the Mixture Screws and have no Air Leaks ...
    You're next step is to check the sizes of the Jets and make sure that somebody didn't throw-in whatever happened to be handy to: "Just get it running" in order to sell it.

    Look CLOSELY at the Plugs; too!
    If the Ceramic is eroding or there is ANY evidence that the Ceramic's are getting little tiny stress fractures around them ... you're WAY too Lean and that isn't good for the engine.

    Also keep an eye on the Oil Level.
    If you are way too Lean the Engine will burn the Oil Sheen that belongs on the Cylinder Walls for Fuel.
    This will cause the Rings to wear prematurely and Compression will suffer or be lost.

    The Pistons are aluminum and can't handle the extraordinarily high temperatures that occur during a critically Lean Burn.
    It is possible for critically lean Mixtures to create a Combustion temperature that will melt a hole right through the top of a Piston Crown.
     
  10. mfchapman

    mfchapman Member

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    Rick,


    Is enlarging the jets an option? Would it likely be the smaller of the two that would need to be larger? Why would I get color on the plugs intermittently?
     
  11. RickCoMatic

    RickCoMatic Well-Known Member

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    Sure, running a hotter Jet IS an option. But, if it's the Passages that are clogged and not the Jets ... a fire hose nozzle sized Jet wouldn't help.

    Here's what I do.
    I use a Rubber "Ear cleansing syringe" ... available at any Drug Store.
    I collect Carb Cleaner Spray in a Yogurt Cup.
    Fill-up the Syringe and flush the Passages.

    First, from the bottom -- up.
    Pull the Pilot Jet and Mixture Screw with all four pieces.
    (Screw, spring, flat washer and O-ring)
    Fill-up the Syringe.
    Insert it into the Pilot FUEL Jet hole (with Fuel Jet OUT)
    Squeeze a generous amount aof Carb Cleaner through the Passage.

    It should exit from BOTH the Pilot AIR Jet and some from the Mixture Screw hole.

    Second.
    Re-fill and shoot a generous quantity through the Pilot AIR Jet.
    If you wiggle the thing around jusut right you don't have to pull the AIR Jet.

    Next:
    Take a 1-1/2 inch piece of Vacuum Line and secure it to the end of the Syringe.
    Put the hose into the top of the Pilot Mixture Screw hole.
    Same deal.
    Flush it out good.
    (Block the hole off at the other end of the Pilot Mixture Screw housing where it bleeds into the Intake ahead of the Butteryfly. Use your finger.)
    You should get Carb Cleaner coming out the AIR Jet hole AND the FUEL Jet hole.

    Lastly:
    Fill-'er-up again.
    This time ... squeeze the Carb Cleaner into the Passage to fill the Passages.
    Then, before it all leaks-out ... evacuate the Syringe and insert it into the Pilot FUEL Jet hole and suck-out all the Cleaner in the Passages.

    Finally, evacuate the Syringe onto 3 or 4 squares of paper towel folded neatly.
    Look at the Cleaner you sucked-out of the Passage.
    If there's any discoloration, particulate or black specks on the paper towel.

    Do it all over again until theres nothing coming out you didn't squirt in!
     
  12. mfchapman

    mfchapman Member

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    Sounds like a rainy day project, I'll try it. Quick update: revved bike to 4-5k for 15 seconds then checked plugs and actually got some nice brown! However, not enough color for 4.5 turns out I would think and they are still white when I kill the engine at 55 mph and 5k RPM.

    Thanks man
     
  13. wizard

    wizard Active Member

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    have you had the screws out & checked that all the components are in there & in the right order?
     
  14. mfchapman

    mfchapman Member

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    I have not, however given the difficulty I had removing the caps which covered the screws and the relative ease their movement up and down their respective threads (except one) I am sort of assuming I am their first tweaker.

    Thanks wizard
     
  15. RickCoMatic

    RickCoMatic Well-Known Member

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    Those Pilot Screws are too far out.
    Somethings still not right.

    If you have them at 4 Turns Out ... they will be so loose in there that you won't keep a setting because they'll move with constant vibration.

    The Spring is what puts a load on the Screw to not move.
    Go too far out and there's no "Spring-Load" to keep the Screw from just turning by itself until it pops-out and gets lost.

    You'd be better off running a larger Pilot FUEL Jet and having to keep the Pilot Mixture Screws at something in the 2-Turns area or less.
     

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