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Homemade manometer.

Discussion in 'XJ DIY How-To Instructions' started by Huntchuks, Jan 4, 2020.

  1. Huntchuks

    Huntchuks Active Member

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    Well, while I am waiting for warmer weather to work on further tuning outside, I will be making tools for the process. Yesterday I finished the synchronizer project. When I do a project I tend to overdo it so I thought I'd share the result. I had some mercury from some old lights (sodium vapor I think) and decided to use it instead of colored water or tranny fluid.

    First off was cutting from an old laminated shelf and using a table saw cutting appropriately spaced grooves for the tubing. I decided to make them narrower than the tubing diameter so they would be pressed in and not require any type of holding devices or clips. They are also deep enough so that only a small portion of the tubing is above the surface once installed. Then I masked off the laminated surfaces and hit it with white paint.
    20200103_161649.jpg
     
  2. Huntchuks

    Huntchuks Active Member

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    Next, I darkened lines on graph paper to use as a gauge behind the tubing.

    20200103_163439.jpg

    I decided that every line darkened was not too busy.

    20200103_164154.jpg

    Test to see how it looks behind tubing.

    20200103_174604.jpg

    Now to glue the paper strips in the slots making sure they are all aligned perfectly.
     
  3. Huntchuks

    Huntchuks Active Member

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    Cut and drill holes for a base with feet. The base will also butt right up to the bottom of the F connectors that will connect the tubes.

    20200103_191630.jpg 20200103_191743.jpg
     
  4. Huntchuks

    Huntchuks Active Member

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    OK, skip right to the assembled and filled product. Notice the quick and dirty caps on the vacuum restrictors.

    20200103_200047.jpg

    20200103_200121.jpg

    20200103_200057.jpg
     
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  5. XJ550H

    XJ550H Well-Known Member Premium Member

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    very nice setup. did you use mercury?
    do you think it will work with atf?
     
  6. Huntchuks

    Huntchuks Active Member

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    I used the mercury I had on hand and I realize most people would not have it. That is why it is a unique project. The same design would work with ATF fluid but I would make it twice as tall. I just guessed at the height of mine but figured if I kept the mercury level fairly low, and because it is so dense, I wouldn't have an issue with it being sucked into the engine. When I first try it I will also have plenty of extra tubing above the connectors just to make sure!
     
  7. Franz

    Franz Well-Known Member

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    Looks great be interesting to a see a video of them when you set up the carburettors.
     
  8. ManBot13

    ManBot13 Well-Known Member Premium Member

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    In response to ATF vs Hg, Hg is 13 times more dense than water, and even a little more dense on top of that than ATF. So a pressure difference that causes a change in Hg height of 1 inch will move ATF well over a foot.

    Engines might draw 20 inHg vacuum, so that’s the maximum a column could move (20 inches). Again ATF could move over 20ft for the same vacuum reading. Mind you we are actually looking at differential pressure which much smaller when syncing.

    That’s the reason why Hg was the original fluid to measure pressure, you don’t need a 20ft column to measure it. But Hg is very toxic and that’s why it’s not used readily.
     
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  9. Polock

    Polock Well-Known Member

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    two glass bottles is cheaper and more accurate
     
  10. Huntchuks

    Huntchuks Active Member

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    I got itching to try the manometer even though other work needs to be done before the real syncing. I have only bench synced till now, so the video only shows that in the levels. No synchronizing is done in this short clip, rather the test is to see how the device works. I am having issues with a touchy throttle and it is taking some time for the RPM's to come back down. Frustrating.

    Edit: I just checked the throttle linkage and when I release the throttle the cable goes slack but the throttle shaft returns more slowly. This cooler weather may affect the silicone paste I used on the seals/shafts. Looks like I'll need to remove and break them apart again. What a pain, but, the manometer works!

     
    Last edited: Jan 13, 2020
  11. Huntchuks

    Huntchuks Active Member

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    Upon further inspection I discovered the main spring was not mounted to the right spot by comparing my pre-disassembly pictures to the current assembly. This makes the spring not wound quite enough. Not sure how I goofed the assembly. Pulled the carbs and will do a complete inspection.
     
  12. Huntchuks

    Huntchuks Active Member

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    I removed the butterfly plates to see if they needed repositioning. No matter how I replace them I can always see a sliver of light, shined from the other side, somewhere. Has everyone else been able to do this completely?
     
  13. XJ550H

    XJ550H Well-Known Member Premium Member

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    thats how you know they are installed correctly a sliver of light.
    now you need to bench sync them
     
  14. Huntchuks

    Huntchuks Active Member

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    I assumed when closed completely they should actually be completely closed, before bench syncing. Are the plates not capable of completely filling the cavity at that angle? If both were perfectly round it would be impossible unless the plate was able to be 90 degrees (flat) from the sides all around. That is obviously not the case.
     
  15. XJ550H

    XJ550H Well-Known Member Premium Member

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    plates are a smaller diameter than carb throat. the reason you want to see a cresent of light is so you know plate is centered on shaft
     
  16. Huntchuks

    Huntchuks Active Member

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    Maybe I should have measured the diameter of a plate. Are they not round? They fit side to side but not top to bottom. That would make the fit imperfect and there would be slivers of light at the four 'corners ' when fully closed. Is this correct?
     
  17. jayrodoh

    jayrodoh YimYam Premium Member

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    They are not perfectly round and only properly fit one way. Imagine cutting a tube at an angle and then setting the cut end on a piece of paper and tracing the outside. You will end up with an oval. When assembling carbs I like to leave the screws holding the plates slightly loose and then let the throttle snap shut a few times with the idle stop backed all the way out. This will align the plates into the bores. Tighten the screws while they are seated and the throttle stop backed out.
     
  18. Huntchuks

    Huntchuks Active Member

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    Thanks, that is how I tightened the screws, the best way I could think of. Then I could still see light from a flashlight from the other side and thought there might be a better way.
     
  19. Polock

    Polock Well-Known Member

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    the plates have to be open for it to run
    as soon as you adjust the idle they'll be open even more, then the running sync takes care of any differences
    your good
     
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  20. Huntchuks

    Huntchuks Active Member

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    I modified the manometer a bit. Removed the clear, stiff tubing and replaced with flexible, heat resistant silicone. Added clamps everywhere to reduce the possibility of vacuum leaks.Kept a short piece of clear tubing at the top so I could move the vacuum restrictors there so they are more easily removed for modification.
    20200415_171045.jpg
     

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