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Running sync: screw in or out, that is the question

Discussion in 'XJ Technical Chat' started by quebecois59, Nov 10, 2015.

  1. quebecois59

    quebecois59 Well-Known Member

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    I realize today that I didn't have a clue about which way to turn sync screws to have to right result while performing a running sync. In other words, if I want to give more vacuum to carb #3, do I have to screw in or out?

    I thought i may not be the only one so I decide to share a few pictures with the forum.

    To answer this, I put a carb rackI have on the shelf. Here is a general view:

    general.JPG

    Let's do it in the same order recommended in the manual, starting with carbs #1 and #2. If your vacuum gauges show that #1 sucks less than #2 , you should do this:

    carb1+2.JPG

    Second, we should balance carbs #3 and #4. If readings are lower for carb #4, you should do this:

    carb3+4.JPG

    Finally, to balance 1-2 pair with 3-4 pair, if 1-2 pair readings are lower , you should do this:

    balancing- pairs.JPG

    In other terms, first and second sync seem counter-intuitive, if you want more vacuum on the left , turn to the right. The third one is intuitive, if you want more vacuum on the right, turn to right.

    I hope it could help.
     
  2. k-moe

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

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    You'll see right away if you turned the screw in the direction that you need to.
    Nice job making it clear on which screws control which carbs.
     
  3. Polock

    Polock Well-Known Member

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    actually you need to make #4 match #3. #3 is controlled by the idle screw
     
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  4. quebecois59

    quebecois59 Well-Known Member

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    The way I understand it, the idle knob controls all butterflies opening at the same time.
     
  5. XJ550H

    XJ550H Well-Known Member Premium Member

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    yes it does move them all, but it sets #3 as the base point idle for the start of the sync. then the screw on far right sets 4 to match 3.
    you can not match 3 to 4 by turning a screw or idle knob. the screw on 3 matches 1&2 set to 3&4 set.
    turning screw 3 opens and closes 4.
    great photos. I understand what you mean in the drawings, i think what is being said to your statment over the photos is
    "Second, we should balance carbs #3 and #4. If readings are lower for carb #4, you should do this:"
    you could have added if readings are high turn in opposite direction..
    you did get the point across, and I would hope any one syncing could infer how to turn when reading is high.
     
  6. hogfiddles

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

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    Sync screws arent " In vs. Out ". They are " left vs. right " or " one vs.the other". Doesn't matter..... Turn the screw between 3&4. If the levels get closer, you're turn the needed direction.... If the levels get farther apart, turn the other direction.. Same procedure for 1&2, then Same procedure for left half and right half. It's very intuitive..... Really shouldn't take more than a few minutes.

    Turn the screw a tiny bit, let go and blip the throttle. Let the idle settle, see where it is. Continue--- adjust, blip, watch, adjust, blip, watch, etc....
     
  7. quebecois59

    quebecois59 Well-Known Member

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    You're right, but I like to know what I'm doing before I begin something.

    I used the terms "in" and "out" because every body who has already used a screwdriver would know what I mean.
     
  8. eurosnap53

    eurosnap53 Member

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    Lol
     
  9. quebecois59

    quebecois59 Well-Known Member

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    I just performed my running sync. I was probably a bit stressed out because it seemed everything was exactly the opposite of what I wrote yesterday, Oh well !

    Anyhow, I used my home-made sync tool:

    Carb balancing tool.JPG

    There is none is the tubes on the picture but they were all a bit less than half filled with ATF. Each tube has a restrictor that you can't see on the picture (I should update that picture !). It worked pretty well, the liquid didn't creep to fast (I have at least 6 feet of tubing betwwen the top of the board and the carbs), so I had plenty of time to adjust. I did a bench sync a few months ago, so each pair wasn't actually badly out of sync, #1 was like #2 , and #3 was almost like #4, but left pair and right pair were not balanced at all (right pair sucked more vacuum).. I had to speed up idle with the knob at a point or the bile would have stalled when I tried to balance left and right. But in the end, I got them all equal.

    I took the bike for a 40 km ride then. I had to slow down idle a bitit idled at 1200 after the ride.

    I amaze with how the Seca900 handles like a small bike but performs like a big bike.
     
  10. XJ550H

    XJ550H Well-Known Member Premium Member

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    nice setup .are the right side and left side connected ?
    will you do an assembly drawing with details?
     
  11. Polock

    Polock Well-Known Member

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    now that you've done it, do you see that it takes longer to explain it than to do it ?
     
  12. quebecois59

    quebecois59 Well-Known Member

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    Yes they are connected at the bottom. I will put a few more pictures later this week. I'm pretty sure I made ie according to a plan and instructions I found on this forum 2-3 years ago, actually
     
  13. rocs82650

    rocs82650 Well-Known Member Premium Member

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    Good job.

    Gary H.
     
  14. quebecois59

    quebecois59 Well-Known Member

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    Well, lots of things are like that in life ! For fun, just try to explain how to throw a baseball, you'll be surprised...just kidding.

    Actually the setup was a bit longer than the sync itself, because my tool is made of tubing a bit too big to fit the vacuum nipples on top of carbs, so I had to be inventive.
     
  15. quebecois59

    quebecois59 Well-Known Member

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    I can't find the plan I used to make my sync tool. Here is a pic of one of the restrictors:

    restrictor closeup.JPG

    It is simply a tube connector with a section of a small spray tube slipped in and epoxy-glued in it.

    As for the drawing with details for the whole tool, I think I'll use some pictures and I'll write measurements on them.
     
  16. Busted Knuckles

    Busted Knuckles Member

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    I just threw in some MIG welder tips into the tubing.

    Curious how my carbs look after the rebuild. Before, the ATF was all over the place. Hoping after the top end rebuild and the bench sync the carbs should be in a little better shape.
     
  17. quebecois59

    quebecois59 Well-Known Member

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    Anything that would restrict the flow of air should do the trick, the liquid will bounce a lot less, making the adjustments a lot easier. The bench sync is essential too.
     
  18. cds1984

    cds1984 Active Member

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    I love the subject line.
    For some reason it makes me think of the Karate Kid. :)
    For what its worth... I use my electronic carbmate from either side or any side for the same results!
    XJ FTW!
     
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  19. quebecois59

    quebecois59 Well-Known Member

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    Here is the bottom part of the sync tool:

    sync tool bottom.jpg

    Damn** it, again I have a picture that doesn't want to cooperate...

    All you need is four T connectors and to blind plugs. I used small t-wraps to secure the connections, and some tiny wire to hold the connectors and the tubes themselves to the plywood board.

    I didn't measure them accurately , but I'd estimate that each tube is 7 feet long, the borad itself is 4 feet long.

    I put the restrictors in the top section, but they could be locate anywhere I guess:

    Sync tool top.jpg

    My tubes are a bit too big to fit the carb nipples perfectly so I had to insert short sections of smaller tubing, even then is wasn't a 100% tight fit when the tubing got hot.
     
  20. quebecois59

    quebecois59 Well-Known Member

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    balancing- pairs.JPG

    I forgot to show clearly the idle knob location.
     

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