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took the carbs to church and now I cant get the bike to start

Discussion in 'XJ Technical Chat' started by NikoRx, Mar 1, 2020.

  1. Minimutly

    Minimutly Well-Known Member

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    Have you not listened? Vacuum leaks? And you think as if it's OK to leave the vacuum pipe open while trying to run the engine? Some thought on your part might not go amis here.... come back with your thoughts on this?
    And you haven't turned out the "air mixture screws" out at all yet? They aren't air mixture screws, they are mixture screws, start introducing "air" into it and you could confuse them with air screws, which do the same things, and don't exist on this engine, but in the opposite way - d'you see where this could lead?
    So put the mixture screws 3 turns out, start the bike, reduce the enrichment - you might not even need it to start. Once running without enrichment you can do a running sync. If the engine doesn't run without enrichment screw them mixture screws all back out some more until it does.
    Magic doesn't happen, it's all logical, but you have to understand the process.
     
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  2. NikoRx

    NikoRx Member

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    The vacuum leak was happening when I had the fuel tank hooked up and wasn't using an auxiliary tank so when I finally switched over I had neglected that part until yesterday.

    I double checked for vacuum leaks with the vacuum pipe closed and it did not take off when I sprayed starter fluid around the carbs so there is that positive note.

    I sincerely thank you for the bluntness of your messages. The mixture screws are set at two and a half rotations out while I have been working on it this go around. Also earlier in the thread I saw where it can sometimes be 5 full rotations for the idle screw to be turned out on these carbs. It has been difficult to measure since I have to use a screw driver to adjust it but once work is done I am going to give it another go.
     
  3. Minimutly

    Minimutly Well-Known Member

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    Here you go then, screwdrivers have been used since mixture screws were invented. This is how you do it.
    Mark your screwdriver, if it doesn't have a makers mark on it. Place it in the slot, somewhere you can see this marking. Turn it out, counting revolutions - in this instance, to make this easy, go for 3 turns. Anything in between you just guesstimate.
    Apologies for being blunt, but two pages in and your still asking silly questions instead of riding - people will lose interest, and you'll get no help.
    Krack on, and come back to tell us it's running and you've done a running sync, and it idles smooth as anything.
     
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  4. NikoRx

    NikoRx Member

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    Taking apart the spark plugs and look what I found! 1 is the closest and 4 the furthest away. I can smell gas in the first two but not the second two. Taking the carbs off and doing a thorough recleaning of the fuel passages
     

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  5. NikoRx

    NikoRx Member

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    Ran a compression test with the carbs off and the bike wasn’t at operating temps.
    4 is 175
    3 is 165
    2 is 170
    1 is 170
    Manual says it is supposed to be 130-160 psi, I feel like the good news is that I don’t have to replace any rings or bores. Could my valve clearance be an issue? I put those into spec last summer but will be doing a quadruple check when I take the top off to fix a small leak in the gasket.

    mom another positive note @XJ550H helped me solve the case of the mystery wire which turned out to be the low oil switch. The wire diagram has that marked as if it is supposed to be a black wire with red stripe, not a white one.

    going to check the coils next, I have spark with all four plugs but it doesn’t hurt to be thorough

    EDIT: I got 2.7 ohms for both coils but got diddly squat for both of them on the second test between the coil and caps. How am I getting a spark If I’m not getting a reading? Watched a YouTube video on top of reading the manual on how to test it
     
    Last edited: Jun 2, 2020
  6. XJ550H

    XJ550H Well-Known Member Premium Member

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    plug wires are 21K ohms with caps on turn the dial on the meter to higher setting
     
  7. NikoRx

    NikoRx Member

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    Still no reading
     
  8. XJ550H

    XJ550H Well-Known Member Premium Member

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    remove the caps the cap unscrews from wire cap could be bad or end of plug wire may be corroded trim wire back about 1/4 inch.
    wires should read 11k with each cap at 5k ohms.

    if they are oem caps youu will see a slot in the spark plug side snug it up there is a resistoe in there thats replacable.
     
  9. NikoRx

    NikoRx Member

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    thanks, I actually tried this after your earlier post. The wires still had no reading and I am sure that the caps on the Xj550 are 10k ohms, my readings were 8,8,10, and nothing on my 3rd cap so I guess I need to replace both coils and one of my caps, I will probably just replace all of them, but you say there is a little slot that I can just replace instead of all the caps? hmmm I will look into trimming the wire back and see if that does anything.
     
  10. SQLGuy

    SQLGuy Well-Known Member

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    Replacement NGK caps are a few bucks a piece. I hadn't heard of being able to just replace the resistors. That's cool... but how much would an OE resistor run, if it's even available?
     
  11. NikoRx

    NikoRx Member

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    @SQLGuy funny that you just dropped in, I was reading up on your TCI write up!
     
  12. XJ550H

    XJ550H Well-Known Member Premium Member

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    more than replacment caps
     
  13. NikoRx

    NikoRx Member

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    So I have some high compression test readings and am purchasing a leak down tester to check the seals. I would prefer to not break down the engine, is there a way to safely clean the combustion chamber? I see chemicals for it but do i just spray it into the combustion chamber and try to run the bike? I am having idle issues. Of course this is a moot point if the leak test fails.
     
  14. XJ550H

    XJ550H Well-Known Member Premium Member

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    there is a thread where atf was sucked in through the nipples to clean out the carbon. seafoam has videos of doing the same thing.

    using seafoam in fuel tank will also help
     
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  15. hogfiddles

    hogfiddles XJ-Wizard, Host-Central NY Carb Clinic Moderator Premium Member

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    That is your petcock vacuum line. Cap it when there is no petcock connected to it
     
  16. hogfiddles

    hogfiddles XJ-Wizard, Host-Central NY Carb Clinic Moderator Premium Member

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    What chart did you use for you valve clearances?
    What were your clearances?
    What shim were in it?
    What shims are in it now?
    What are your current clearances?
     
  17. SQLGuy

    SQLGuy Well-Known Member

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    I have heard of places that do walnut shell blasting through the spark plug hole and/or intake, to clean carbon out of combustion chambers. I've also heard of spraying a small amount of water into a running engine to do this. I haven't tried either and don't know if they're good ideas.

    When I did a valve job on the GPz 750 I used to have, I used a soda blaster to remove the carbon. It did a great job. But that was with the head off, of course.
     
  18. NikoRx

    NikoRx Member

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    Used a chart that I believe you posted in your diy thread,
    Exhaust clearances from last summer
    .09 .013 0.11 0.11
    Intake clearance
    0.06 0.14 0.09 0.12

    shims exhaust
    265. 265. 260. 265.
    Intake
    270. 265. 280. 275.

    I can’t remember from my sheet if the first numbers I wrote down were the original whim numbers or my first estimates, I remember having messed one or two up but my circled numbers were definitely final measurements and shims

    and now that I look at it a few of those numbers make no sense as to why I wrote them down... I’m taking the dang thing off tomorrow and remeasuring. Standby for update on the the clearances, pretty confident about the shin numbers though
     
  19. hogfiddles

    hogfiddles XJ-Wizard, Host-Central NY Carb Clinic Moderator Premium Member

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    Exhausts are all waay tight, and only 2 intakes are in spec
     
  20. NikoRx

    NikoRx Member

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    Those were the original clearances and I am remeasuring as I type this. My question is should I measure from sliding it into the side of the lobes or what I can push down into it?
     

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