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Manometer gauges

Discussion in 'XJ Technical Chat' started by Scrape, Jun 14, 2007.

  1. Scrape

    Scrape Member

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    As everyone knows, manometer gauges are expensive. I'm new to this so bear with me because I have 3 questions.....Thank you for any help!

    (1) Can't I just use 2 gauges by putting a tee on them...use one gauge for #1 & #3 and the other gauge for #2 & #4 ? I could just put valves on each of the lines or just pinch off good the 2 lines that I don't want to use.

    (2) What would be a safe, average, rough estimate of the vacuum readings that I should be getting....as in high and low so I can buy a gauge that is sensitive enough to read fine adjustments?

    (3) I can remember reading somewhere here, can't find it now when I need it, that I have to restrict the flow in each vacuum line by connecting in a smaller diameter tube section. I guess the vacuum pulses and it can make the gauge act irratic?...I haven't a clue. I guess the more accurate the gauge is, the more erratic it would be if this happens. Maybe it would bury the needle on the gauge all the time too. Is this going to be some big issue when I put this thing together or can I just connect the vacuum lines up and call it done?

    I might go try Graingers today to buy the gauges that I need to sync the carbs.
     
  2. Fraps

    Fraps Member

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    Hi Scrape.

    I purchased a manometer gauge (just one) to see how effective it would work. It cost about $20 CAN and comes with the port restricted. You can buy other gauges for cheaper without the restriction - but then you'll have to add it.

    1. The purpose of the gauge is to equalize vacuum on each individual carb. On your proposed setup, your #1 carb may be drawing way too much vacuum and #3 carb way to little and there is no way you would know. You can use 2 gauges though, first on #1 and #2, then on #3 and #4 and finally between bank#1,2 and #3,4.

    2. High or low, you want them to be the same. The gauge is going to jump around way to much for you to "accurately" read it.

    3. Erratic is an understatement. My gauge is now collecting dust because I find it useless! I use either a U tube manometer or my newest kick - the bottle manometer.

    If you are dead set on the gauges, maybe start out with one as I did and see how you like it before spending too much on multiple gauges.

    I hope this helps.
    Good tuning!
     
  3. Scrape

    Scrape Member

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    Thanks Fraps...you were a great help. If I can at least read the high and low points on the vacuum modulation, maybe the mean or half way point will suffice for a value to follow as a reading to use...just as long as I do them all the same. I have to think more on this and may do a test run, like you said, on a gauge that will show a large range of modulation. I may just get a needle valve to adjust the restriction too and see what animal I'm dealing with here.
     
  4. Scrape

    Scrape Member

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    I'm also wondering that if I don't use the YICS tool, I hate to even contemplate it, modulation might be decreased or relieved some. I would think that it may require an extra round of sync to get them right without the YICS tool. The fact is that the other carbs that aren't tweaked together yet would be effecting the readings being connected by the YICS passage. I do like the thought of maybe rechecking the sync anyway after the YICS tool is removed. I do believe that this may lend clues as to maybe one of the YICS passages being restricted or blocked. It is the real environment / arena that these carbs operate under and the true condition that they see. I can see why some butt heads over using the tool or not...even if the factory manual says to use it. This stuff if way above my level of knowledge right now but I am in question as I think about this stuff for the first time.
     
  5. Fraps

    Fraps Member

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    The easy way to do it is by preference. Synch with the YICS tool and run your bike. Then synch without and run your bike. Either you will notice a difference or not. If you do notice a difference, go with your preference. Simple.
     
  6. Captainkirk

    Captainkirk Member

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    The debate over whether to use the YICS tool will likely rage as long as there are XJs that run. I prefer to use it; this is what the factory manual as well as the Clymer manual recommend and I see no reason to deviate. There are links to plans on this site. I constructed my own and it works as well and as quickly as the factory tool (no aggravating, slow wing nuts!) and it didn't cost a fortune.
    You can purchase an "economy" manometer through Motion Pro for under $50.00 through Dennis Kirk and other suppliers. I chose the professional model, spent a little more on it, with this thought in mind;
    You don't just synch carbs once and let it go. You synch them every season, at least, and any time you tune up the bike or fiddle with any carb adjustments. A good set of manometers may outlive the bike you ride now, and can be used on any carbed bike you may buy in the future. It's my opinion (and mine alone, mind you) that carb sticks are a critical piece of equipment that gets used often, and you should invest in a high quality example, rather than just cobble something together in the interest of saving a few bucks. Well-tuned carbs can mean the difference between a dog of a bike that just runs, and a well-tuned machine that responds as quick as you can think. I'm sure there are those who differ, and they certainly are entitled to their opinions; I'm just stating mine.
     
  7. Robert

    Robert Active Member

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    Scrape, you can find a reasonably prices set of gauges from JC Whitney. They will run you about $50 and come with everything you need to sync your bike right (save the YICS tool if you need it, that you have to build/buy separately). I've used the set of gauges I bought from them for over 15 years and they are just fine. I had to replace the rubber hoses a few years ago because of old age but that was rather expected.
     
  8. RickCoMatic

    RickCoMatic Well-Known Member

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    All you need to do is fabricate some restricters.
    Simple.
    Get some of those plastic pieces used to join two hoses. (Unions)
    Stick a Carb Cleaner Red Tube all the way through it.
    Stuff the Union with Epoxy and let it cure.
    When the Epoxy sets-up ... clip the ends off. Now you have a very, very narrow passage.
    Stick this restrictor in a short piece of hose and connect it to the vacuum port to take the vacuum reading.
    Connect the guage to the restrictor.
    Now, there's MUCH, much less fluctuation in the Vacuum gauge.

    Use ONE guage to do the whole rack.
    Measure the Vacuum of #-3 (Adjust 3 with the Idle Adjust Rod)
    Mark the MAXIMUM vacuum reading of 3 ... right on the guage ... with a sliver of masking tape.
    Block off 3 and read 4
    Adjust 4 to where your tape is marking the exact vacuum of 3.
    Block off 4
    Do 2.
    Mark 2 ... don't match it yet.
    Block off 2
    Do 1
    Match 1 to the mark you got doing 2
    Block 1
    Now match 2 ... to 3.
    1 is attached to 2 ... goes along for the ride when you Match 2 to 3!
    Your sync'd.

    One guage ... four carbs ... perfect sync.
    Make the restrictor.
    You need it.

    Welcome to OLD SCHOOL!
     

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  9. KiwiXJ750D

    KiwiXJ750D Member

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    I have used both the Morgan Carbtune II (borrowed of Dave Jackson) and my $5 bit-o tube 'n 2 stroke oil home made tool (suggested faq section) to sync my EFI and set of carbs. If anything the $5 tool was more accurate as it was more sensitive to very slight changes. Both gave great results.

    YICS tool not used either time, next time I am going to try Rick's clothes line trick to see if that makes a difference for good or bad and maybe borrow Dave's YICS tool (that he doesn't use).
     

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  10. Scrape

    Scrape Member

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    Sweet!!!!!! :D I think my manometer decisions are complete and I'm on the road to a check mark on my list of things to learn and do. I want to use a gauge and, in my early stages as a member here, have seen/read about the U tube and bottle manometers out there, that Fraps mentioned. I like the thought of one gauge reading all 4 carbs due to my anal fears of hysteresis and calibration issues with gauges. I'm sure I am just being foolish with that concern but one high quality gauge will get the job done right, like Captainkirk expressed. Rick, I know that it was one of your past posts that I read about the carb cleaner tube restricter. That's where I faintly remember learning about needing one and this is exactly what I am going to do when I make my manometer. Thanks for repeating this information...I am grateful! I also appreciate the procedure of sync with one gauge also.
    I sprung the bucks on a professional Morgan colortune kit with 4-12mm plugs the other day, so that one is in the bag now and ready to check off my list. I was a bit hasty to get the order off and didn't research the comparison to various brands but I hope they are quality units and I did the right thing. I like the idea of all the plugs being the same when tweaking the combustion and it is a whole lot faster too. :) Now all I have to do, in the short run, is to get my valve clearance measurements done to get my shim and valve cover gasket/bolt O rings order in the mail. During the winter, the carbs are getting rebuilt and the bike will be top shelf. I have to check the compression also yet and have to buy that tester next to complete my checklist. :( I can't forget the wire/Mystery oil and 1/4 inch rope either...I know I have all that stuff around here somewhere! :wink: Thanks again for helping to see me through this journey....I am a better man because of it!
     
  11. Scrape

    Scrape Member

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    I think I'd go with the home made one too Kiwi...I'm paranoid of sucking the mercury in the carbs, from what I have read. I may give that manometer design a try also in my spare time one of these days to see which one I like better. I have to tweak myself in just like the bike. :lol:
     
  12. KiwiXJ750D

    KiwiXJ750D Member

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    Bench sync the carbs then you should not have too much of a problem. :) 2 stroke oil won't hurt the engine if it gets sucked through, your carbs would have to be "way out" to suck that much 8O . You can adapt my design to work on all four carbs using 2 T joins at the bottom, but it is far less confusing to do a pair at a time :wink: . Only cost a few dollars (if that), easy to use, anyone can make one, anyone can afford one, so there is no reason anyone's XJ should be out of sync! :)

    That's the Kiwi way!
     
  13. Captainkirk

    Captainkirk Member

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    You won't be in danger of "sucking the mercury" into the carbs unless you blip the throttle hard while synching.....and you don't want to do that. There's no NEED to do that. Vacuum readings are taken and adjustments made at idle only. All you're trying to do (in a nutshell) is equalize (synchronize) the airflow across the throttle plates (at idle)......once synch'd, the rest takes care of itself.
     
  14. stereomind

    stereomind Active Member

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    I found that when using a generic vacuum gauge, you can eliminate the needle dance by gently pinching the vacuum tube. The more you pinch, the closer the gauge will get to the correct reading. Works sorta like Rick's restrictor plug.
     

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