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Old School Method of One Vacuum Gauge Carb Sync

Discussion in 'XJ DIY How-To Instructions' started by RickCoMatic, Sep 16, 2006.

  1. RickCoMatic

    RickCoMatic Well-Known Member

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    I suppose it won't be too very long before somebody comes-out with a Carb Synchronizer Tool that's all digital, solar powered, with a combined LED and numeric read-out, that will fit in your shirt pocket. Until then; columns of mercury or the handy, new, stainless steel-weighted synchronizers are the way to go.

    But, for XJ-Owners, who are only going to sync-up the carbs every couple of decades ... or, for those who don't want to lay-out seventy-five to a hundred bucks (or more) for Carb Sticks or a CarbTune meter ... buying an expensive meter, or one filled with mercury just isn't practical for as often as you'd ever need to use it.

    So ..., how are you going to be able to get your Carbs synchronized without buying the Sticks, or taking your bike to someone who's got sticks, or to a place that charges big-bucks to do something you'd do for yourself ... if you had the means?

    ! ! ! ! ! ! ! ! ! !

    Easy ... Just hop in RickCoMatic's Time Machine, and come back with me, to the time before Carb Sticks; when you had to "Match-up and Sync the whole rack ... with ONE Vacuum Gauge!

    The Old School Method
    Single Vacuum Gauge Synchronizing of Carburetors
    by: Rick Massey
    Special to XJBikes.com
    All rights reserved.

    First, you need one vacuum gauge. (There's none better than the one sold at Sears for $19.95) and your home-made YICS tool.

    A couple of Electric Fans to keep the Old XJ from overheating while you do the tuning-up. Two. Aimed at the Engine. High speed for Max cooling!

    You need some vacuum line. Get ten or twelve feet. You'll be making-up lines to run from each carb out to the side of the bike where you'll hook-up the Vacuum Gauge.

    You need a few small, hollow, plastic-barrel vacuum line connections. (Those little things you use to plug one vacuum line into another.)

    One medium-sized fuel filter; with ends that will fit the hose.

    One red plastic spray tube ... like the one taped to a can of carb cleaner.

    Four regular Golf Tees. (Just steal 'em from your dad's golf bag)

    5-minute epoxy.

    Masking tape and a "Sharpie"

    OK kids ... Let's ROCK!

    Prep:
    Fabrication of the "Vacuum Restriction Valve." (Absolutely necessary)

    Take the skinny red tube and run it through one of the hollow, plastic hose connectors.
    Seal that hollow connector with epoxy; leaving a length of the red tube extended from each end.
    (This fabricated little-metering device will be the all-important "Vacuum Pressure Restrictor" that will allow you to read the vacuum gauge without the extremely WILD fluctuations on the meter you'd get if you tried to get a vacuum reading without it.)

    When the epoxy hardens; cut-off the extraneous ends of the red tube -- flush.

    Using a short length of vac line ... attach the restrictor to one end of the medium-sized fuel filter.

    (Now you have a restrictor attached to the fuel filter. You just made what you NEED to get the needle on the vacuum gauge "Quieted-down" enough to get an accurate reading without the meter being so wildly fluctuating as to be useless. You have Baffled-Restricted-Regulation and this softens the harsh, impossible-to-read fluctuation, the indicator would have, without it.)

    Hook-up and Sync:

    The rest is by the book.
    YICS tool inserted.
    Four Vacuum lines run from the Carb Intakes over to where it will be convenient for you to connect these four lines up to Vacuum Gauge ... each marked with a little tape label for one through four. Stick the golf tees in the ends of these lines ... and get ready to sync the carbs.

    Attach your "Old School - Baffled Restrictor" to the vacuum line coming from Number - 3 with the red tubed restricted end plugged into the vac line coming off the engine.

    Plug the Vacuum Gauge into the Fuel Filter end. You're officially restricted and baffled for testing ...

    So, let's do it!

    Run the bike and get the vacuum reading of Number 3 (Three) ... to check for good vacuum on three and to observe how the needle of the gauge is still going to MODERATELY "Vibrate" as it measures engine vacuum.

    Sneak the rev's up to 14 > 16-hundred rpm's and the fluctuation will become rapid enough for you to read the vacuum that the hole is pulling.

    Mark the gauge face with a short strip of masking tape and mark the tape with a check-mark. Don't let the tape strips block you from seeing the vacuum gauge needle during the sync.

    Authors Note:
    It's a good idea to practice pulling a golf tee out and covering the hose with your thumb. This will keep the engine from stumbling and possibly stalling.

    Checks and adjustments:

    Read the Vacuum being pulled by Number 2. Mark maximum vacuum drawn by 2 with line of tape.

    Get your magic fingers ready to do the "Carb-Shuffle!"

    Pull-out the baffle and block the vacuum with your thumb until you can insert the golf tee you have ready between your lips or behind your ear.

    Measure the vacuum being drawn by Number 1. If the max vacuum being drawn by Number 1 is NOT the same as you have MARKED for Number 2 --ADJUST the SYNC SCREW on Number 1 ... until the Vacuum drawn by ONE is the SAME as the Vacuum drawn by TWO!

    Two down ... two to go! But, here's where it gets tricky.

    Plug-in to Number 4. Set the Vacuum drawn by Number 4 -- to -- the BASE Vacuum you measured for Number 3. (Actually check 3 again ... adjust 4 to match 3 -- because 3 is the Base Vacuum Port, has NO sync screw adjustment, and usually has the petcock vacuum hose connected to it.)

    At this point you start TWEAKING. From here until the rack's in-sync ... it's all down hill!

    The engine should be sounding pretty darn good; right about here. But, we need to finish it off!

    Just hook-up to Number 2, now ... and bring the vacuum being drawn on Number 2 -- UP or DOWN to match the value of Number 3.

    They'll be no need to adjust Number 1. Number 1 is connected to Number 2 and goes right along for the ride when you sync Number 2 to Number 3 ... and you ...

    HEAR the results of synchronizing all four of your carbs with only one vacuum gauge.
    Let what I have outlined, here, be your guide ... but, don't be afraid to get creative with where to have the golf tees ready to pop-in the lines!

    When you wrap-it-up ... the One - through - Four ... Final Measurement should be all right on the same value -- right across the board.
    Yes? DONE!
    No? Tweak until you nail it!

    Can you believe that we used to have to do it this way? Compared to the MotionPro Carb Sticks -- It's like being in Bedrock ... spending a little time with Fred and Barney doin' a little Stone Age Tweaking'!

    You folks are great.
    The quiz is whenever you try it.

    That's our report for this evening ...
    This is Katie Kouric ...
    For CBS News; thank-you;
    and, good night.

    -30-
    Editors Note: Since first published this process can be done even EASIER, ... Using a 4-Valve Aquarium Air Hose Device allowing you to close-off the various lines and do much faster balancing.
     
    Newschoolmedic, kikeat and PavelK313 like this.
  2. SnoSheriff

    SnoSheriff Site Owner Staff Member Administrator

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    Thank you for the writeup RickCoMatic. If anyone has pictures for this process, please attach them here.

    If you guys have a video on doing carb sync or any other maintenance work, I'm willing to resize the file and place in in the "Downloads" section. PM me and we'll go from there...
     
  3. Ace_Frehley

    Ace_Frehley Member

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    Excellent report rick, thanks for the help!
     
  4. OU812didntU

    OU812didntU Member

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    thanks for the old school rendition on carb sync, this carb sync thing is all new to me am a picture guy, whenever anybody explains things to me am like huh!!! i see a pic and its like ohh yeh why didnt you just tell me that. I think am gonna give it a try.

    Question what is this YICS tool????? heard people mention it a few times but have no idea how to make it or what it looks like. probably need to look at a picture.

    thanks
     
    XJ75082 likes this.
  5. MiCarl

    MiCarl Active Member

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    Yamaha Induction Control System. A small passage that connects the four intakes together. I forget the reason for it being there......

    Anyway, the intakes need to be isolated to sync properly. The tool goes into the passage to close off the flow.

    Information on the tool is in this post:

    YICS TOOL
     
  6. RickCoMatic

    RickCoMatic Well-Known Member

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    The YICS tool is a tool you need to separate the for carbs for an accurate sync.

    There's plans for one on the web ... if I could find the link ... and the YICS Theroy; too.

    Search the archives, here, you'll probably findf BOTH.
     
  7. ArizonaSteve

    ArizonaSteve Member

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    It should be mentioned that it's impossible to sync the carbs if the rubber boots have any cracks in them because air leaks will throw off the readings so much that any attempts to sync using the adjustment screws will actually make it worse instead of better.
     
  8. PainterD

    PainterD Active Member

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    So my question is: If the carb synch tool blocks off the little ports when you tighten it up inside the head, then...would it be correct if I just use the correct size rubber hose with a long threaded rod inside it to do the same thing? I found a piece of hose that fits snug inside the head hole (it has to be forced in to get it all the way thru) so that should work with a threaded rod inside it to keep it tight enough to block off the passages. correct?
    That is basically what the YICS tool does anyway. It shouldn't take much to block those little holes to synch the carbs. >PD<
     
  9. RickCoMatic

    RickCoMatic Well-Known Member

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    If the outside diameter of the hose gets expanded enough to seal-off the YICS passage when the threaded rod is inserted into the hose ...

    Yes, I would say that that is the idea and it might work. If an intake leak results from the attempt; the bike might not respond to any tuning attempt and stall. If you really think its doing the trick ... sync-up quick; set the mixes and get done.

    Be careful running the engine too hot and having the hose become semi-permanently installed until you get the hose out of there; somehow!

    This is the first I have ever heard of it.
    Good luck.
    I made the tool. You should too.
    The tool is fun to make if you have the plans and all the hardware.
     
  10. PainterD

    PainterD Active Member

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    Update:
    OK, it works. I used a length of hose to block off the YICS passages with success. The hose is actually from a gas torch with a threaded rod inside of it to tighten it. It is a tight fit and when I tighten the threaded rod, it expands the hose just enough to block the ports. I cut it long enough so I can pull it out when I'm done, because it seems to stick a little when it gets hot.
    I first tried plastic, but ended up having to let the engine cool down to get it out! The plastic one gets hot enough to melt (what was I thinking?) but the rubber one works good.
    *It also helps to coat the YICS tool with silicone spray before installing it and it comes out alot easier when your done.
     
  11. Polock

    Polock Well-Known Member

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    Blasphemy
    someone explain why the YICS tool is necessary
    with it all carbs are separate all set up nice and even, then pull it out and their
    not balanced anymore ?
    why not skip the tool and tune it like it's going to run
    personally i'am not a color tune kind of guy but wouldn't it make sense to color tune with the YICS tool in ?
    with the tool out could a rich #1 and a lean #2 both look good ?
     
  12. DanP

    DanP Member

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    Thought I would add a small illustration of the assembly. Just helps with the visual.
     

    Attached Files:

  13. IkeO

    IkeO Member

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    this is great but i got one one huge question. im really new to this...

    when you say connect the vacume tube to the motor. where on the motor? and how. i have a good idea of where its supposed to go but does anyone have a picture of exactly where your supposed to hook the vaccume tube up to the carbs.

    some extra questions..

    what size vacume tube?
    why do you need the fuel filter? whats its function?
     
  14. RickCoMatic

    RickCoMatic Well-Known Member

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    The Vacuum line hooks-up to the top of the Intake Manifold where there is a Vacuum Nipple covered by a Rubber Cap.

    The Fuel Filter acts as a Baffle ... further softening-out the pulsations of the Manifold as it draws Vacuum.

    Instead of the Vacuum Gauge pulsating wildly ... the needle on the Gauge will fluctuate and give you a reading that you can rely on. Without the Restriction Device and the optional Fuel Filter ... the gauge would fluctuate so wildly that the needle wouldn't give you a reading to be able to mark.

    This method is as accurate at a 4-Pack of gauges or Mercury Sticks. It just takes a lot longer to balance the system because you can only read one Manifold at a time.
     
  15. Ass.Fault

    Ass.Fault Active Member

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    The one rico missed...
    1/4" vacuum tube
     
  16. wink1018

    wink1018 Active Member

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    You know, for the price you spend on the plastic union and epoxy for the restrictor, you could have easily purchased a $1 0.025" welding tip and just shoved it inside the vacuum hose going to your gauge.

    Aside from that, Autozone and Checkers sell what is called an "oriface". It looks just like a white plastic vacuum hose union. But it has a restrictor installed inside. Those, however, sell for about $3 each.
     
  17. RickCoMatic

    RickCoMatic Well-Known Member

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    Didn't know that when I learned how to do the job more than 20 years ago.
    I'm all for making a job easier to do and buying something that will save me some time and money.

    When I needed that restriction device, back in the day ... I had all the stuff to make it right in the drawer of my toolbox, so I just knocked one out and it became part of the tool inventory.

    Easy enough to make if you have the stuff and its done by the time you'd get back from the store with the orifice.
     
  18. leaningleft

    leaningleft Member

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    Possable dumb question. If i could put a manometer on all four carbs would i still have to use a yics tool to sync all carbs.I don't mind building a new tool.Nothing better to do waiting for all this snow to go.I worked on the bike in my basement and it appers to be running good.The idles a bit up and down not to bad.But then i can't run it very long before gassing myself.Plan was to have it out before the end of feb. but then again the snow.
     
  19. wink1018

    wink1018 Active Member

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    Yes you do still have to use the yics tool. That's the only way to completely seperate each carb from one another.
     
  20. RickCoMatic

    RickCoMatic Well-Known Member

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    I still believe the best way to do Sync is with the YICS Tool in place or stuffing the YICS Passage with an Oil-soaked cotton cloth.

    Separating the four Carbs during Sync is absolutely necessary.

    I have backed-off the notion that you must have the YICS Tool in Place (or the Passage stuffed) for setting the Pilot Mixtures.

    With the Throttles Closed -- the YICS Passage isn't affecting the Pilot Air Passage.
    I have done my own Carbs Mixtures without the YICS Tool and have them right on the money.
    I think setting the Mixtures the way the bike is going to run is an accurate an adjustment as you would want.

    I've done a few bikes Pilot Mixtures with the ColorTune Plug with and without the YICS Tool in ... and there wasn't a difference in the set-up.
     

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