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XJ700N Spark Plugs

Discussion in 'XJ Technical Chat' started by Dan Gardner, Jun 18, 2021.

  1. Dan Gardner

    Dan Gardner Well-Known Member Premium Member

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    Somebody should confiscate PO's tools and never let him or her work on anything again.

    I can ALMOST give PO the benefit of the doubt - they may have been a novice mechanic (like many of us here) and made mistakes. All of us noobs make mistakes and hopefully learn from them and move on.

    To me, what is infuriating is that I suspect a lot of these "repairs" where made by "professional" mechanics - so some unsuspecting PO paid good money to have somebody completely cock up their stuff, leaving it running like crap and motivating the PO to sell.

    I'm still waiting for an initial assessment from @hogfiddles on the XJ700N rack, but I wouldn't be surprised to find out that there is something equally whacked out on that rack.

    For now, I will replace the missing pieces on the XJ650J rack and hope for the best. The weird thing is that the XJ650J actually runs pretty well. I really enjoy riding on a daily basis - no problems starting, dying, or anything. Maybe that's a testament to the engineering of these bikes in the first place. They can be pretty whacked out and yet still function. (the XL650J is the bike where I can't seem to get a reading on the secondary side of one of the coils, but it is still running strong, even with the whacked out pilot adjustment screws).
     
  2. Dan Gardner

    Dan Gardner Well-Known Member Premium Member

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    Hope everyone had a great 4th weekend!!
     
  3. hogfiddles

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

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    Dan, I’m finishing up two other racks in line..... one will be done in the next day or two, then yours gets torn down, too— then we’ll know:)

    dfox
     
  4. Mechanic1978

    Mechanic1978 Active Member

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    Not sure if its been covered on here or not yet, but when you do resistance testing, you first need to touch the probes together to find the resistance of the meter you are using, and subsequently subtract this reading from your test readings to get the actual true results. All meters are assembled with potentially different internal circuits, so will have a resistance of their own and do not pertain to your testing scale.

    Ohh and all four plugs seem extremely lean, and gaps are inconsistent. I have not personally seen any of hogfiddles work, but I have bought a carb base from him, spoke a little and read a few of his posts, and I'm confident that you won't be disappointed.

    Do you have a bore scope? You can get a better idea of how it has been running by looking into cylinders and checking the valve surface condition. Plugs can be cleaned and changed, not so easily done to valves. Inside view of the cylinders is like viewing a trees rings, the whole story is in there.

    A cheap HD snake cam can be had from Amazon or ebay cheaply, and plugs into cell phone port. Some even have lights and pic capabilities.
     
    Last edited: Jul 5, 2021
  5. Dan Gardner

    Dan Gardner Well-Known Member Premium Member

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    I have a borescope somewhere. I'm sure I put it somewhere for safe keeping and now I can't find it. I've used it to look into the YICS port before, but not the cylinders.
     
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  6. Dan Gardner

    Dan Gardner Well-Known Member Premium Member

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    Here's what remained of the XJ650J pilot mixture screw o-rings:
    xj650j oring remains.jpg

    New o-rings and washers are on their way from @chacal, and the XJ700N carb rack is on vacation with @hogfiddles, so now that I have copious amounts of spare time on my hands I finished up my KV75 tank refinish project:
    kv75 tank done.jpg
     
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  7. Mechanic1978

    Mechanic1978 Active Member

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    Looks good!
     
  8. Dan Gardner

    Dan Gardner Well-Known Member Premium Member

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    I got the new mixture screw o-rings and washers installed on the XJ650J this weekend. It's better, but it still takes 4~4.5 turns to get an orange flame on the colortune.

    I did a leak check with carb cleaner spray - no leaks detected.

    Must be something inside the carbs we can't see?

    Maybe the wrong jets? Somebody could have re-jetted, but I don't know why they would. Still has stock airbox and exhaust.

    Maybe float heights wrong? Would that effect the mixture that much?
     
  9. Mechanic1978

    Mechanic1978 Active Member

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    Weak spark can still run a cylinder, and not produce... Get an adjustable spark tester and slowly adjust the gap. when it no longer jumps the gap, stop and count the #of turns or measure with a dial caliper. Do all 4, and compare.
     
    Last edited: Jul 12, 2021
  10. Simmy

    Simmy Well-Known Member

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    Sounds about right. Now turn the mixture screw in until you get a nice Bunson burner blue.
    Orange signifies a rich condition, 4-1/2 turns would definitely give you a rich condition.
     
  11. Mechanic1978

    Mechanic1978 Active Member

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    Im sure @hogfiddles can confirm, but if you have the new o ring, washer, and spring in all 4, and you have to turn them out to 4+ turns, there is still some blockage, or fault internal in the carb base.

    you ever put your thumb on a garden hose and use it to control the water spray?

    thats similar to what the screws your adjusting do to the "Air" coning thorough the idle circuit. the farther you turn out the richer it makes the mixture, and vise versa for turning them in. @Simmy is correct in telling you your running rich.

    if you have to turn them out that far something is wrong with that circuit. And, I highly doubt it is the same issue for all 4 carbs.

    is it possible you have the jets in the wrong holes?
     
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  12. hogfiddles

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

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    Yes, agreed. In my experience the only time I might possibly see turns that far out are on 550’s..... they’re a different animal.

    double check to see if you haven’t mixed up the jets. Some of the manuals are incorrect. The air jets under the diaphragm belong in this position:
    The bigger number goes toward the front of the bike
    The smaller number goes toward the driver seat

    If you are working with pods, all bets are off and you are basically on your own
     
  13. Toyobaru866

    Toyobaru866 Active Member

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    I always thought that the idle mixture screws controls the amount of fuel and not air. Did I misunderstood or is it different on others carbs than my BS33's?
     
  14. hogfiddles

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

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    They control the MIXTURE.That means they are controlling both, in a sense. As you turn them out, more fuel is allowed through into the air stream.... as they are turned in less fuel is allowed into the airstream. You are adjusting the MIXTURE
     
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  15. Toyobaru866

    Toyobaru866 Active Member

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    Ok, so it works as I thought, thanks.
     
  16. Dan Gardner

    Dan Gardner Well-Known Member Premium Member

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    OK, I've definitely got more investigation to do with the XJ650J rack.

    Definitely possible that there are misplaced jets. In this case at least it wouldn't be my fault.

    I think I will wait until the XJ700N is back up and running so I have something to ride when I pull that 650 rack off again.

    In the mean time, I may just get some clear tubing and get a read on where the float levels are set while the rack is still on the bike. I have a suspicion that the fuel levels may be low.
     
  17. hogfiddles

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

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    Why.... because THIS rack was SO Low?? Lol
     
  18. Dan Gardner

    Dan Gardner Well-Known Member Premium Member

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    Luckily (or unlucky, depending upon how you look at it), the two bikes came from different places. Maybe the same mechanic "serviced" both racks.

    A couple of times on this XJ650J I've been riding down the road - say 55MPH - while also near the primary/reserve switch off points in the fuel tank. I've pulled up to stop at the stoplight, causing the fuel to slosh forward in the tank, then when I get to the light the engine dies. In other words, starving the carbs just long enough while braking to stop for a light was enough to drain the bowls. At least that's what it seems like. Maybe that's normal.
     
  19. Polock

    Polock Well-Known Member

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    you should pull off the fuel line and see just how long it will idle on what's in the bowls.....quite a while
    i think you have other problems
     
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  20. Dan Gardner

    Dan Gardner Well-Known Member Premium Member

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    Yes, I have a lot of problems.
     

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