Carb vacuum balancing question.

Discussion in 'Airheads' started by bushyb, Dec 7, 2012.

  1. boxerboy81

    boxerboy81 Stay Horizontal

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    Ahh, well spotted. I musta read it too quick:wink:
    The needle jet and the atomiser falling out isn't a problem to be concerned about, and if the atomiser didn't fall out but the nj did, it still wouldn't matter. Gravity rules, but the atomiser might get "stuck" in it's hole but easily dislodged regardless. Here's how they line up, mit o-ring, in my BINGS 11/1981 RS.
    [​IMG]
    #21
  2. _cy_

    _cy_ Long timer

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    unless you've done so many carbs you've lost count (500+ for me) .... do ONE carb at a time. take lots of digital pic's to help during reassembly.

    before taking any adjustable part out. make note of original position. lightly bottom any mixture screw taking note number of turns. this will allow returning carb back to original settings and help in trouble shooting.

    a spray can of Berryman Chemtool with a long nozzle is your friend. carbs have all sorts of tiny openings, orifices, internal passages, etc. goal is to make dead certain each and everyone of them are open and clear. even if you've got access to some nasty carb dip and soaked parts. with glasses on, spray each and every opening to test. if spray comes out other side, you've got proof positive sign orifice/passage is clear. use real carb cleaner to do this with. carb cleaner is formulated specifically to desolve carb gunk.
    #22
  3. bushyb

    bushyb Adventurer

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    Thanks that is just what it looks like, It is the second part from the left that dropped out the needle jet. I also have just read in the Hanes book that they also talk about it dropping out. All O rings are in good condition. I am in any case going to order a new kit that most properly will that about two weeks to get here in this part of the world.<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:eek:ffice:eek:ffice" /><o:p></o:p>
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    I need to satisfy myself that it's this carb giving problems. I thing I will clean it again and re-fit the carb get it warm, close down the idle on the right carb and raise the idling on the left and try the mixture adjustment again. Thanks <o:p></o:p>
    #23
  4. supershaft

    supershaft because I can

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    I am real familiar with these carbs. Idle problem? After a couple of carb checks, I get a leak down tester and listen for a leaking valve. It's very often a huge time saver. They won'tr idle right with even the tiniest valve leak, let alone a bigger one.
    #24
  5. supershaft

    supershaft because I can

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    I forgot to add an important part of my advise: HEARING the leak takes some experience. On the intake side at least and it is usually the intake side that is leaking in my experience, if you are not sure if you are hearing a valve whistle, squirt so brake cleaner in the port. You will hear the bubbling for sure! If you have a leaking intake valve that is! Good luck!
    #25
  6. baloneyskin daddy

    baloneyskin daddy bikaholic

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    Take both carbs off after the motor is warm and do a compression check.
    #26
  7. bushyb

    bushyb Adventurer

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    Thanks, you not the first one to mention this. I am not familiar with just how to do it. Anyway I went and bought new O rings again and have fitted them and reset mixture screw back to recommendations of 1 -1/4 turns out. This causes a miss on both exhausts. I the adjusted them by ear out to the highest idle on each carb. This was done without the throttle and choke cables connected and the idle screw adjusted way out.... <o:p></o:p>
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    The bike idles nice and constant but a tad too high about 1100 rpm??? The left carb is better but you can just about close the mixture screw all the way in before it faulters to die.<o:p></o:p>
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    I then use a single dial vacuum gauge to check and compare the reading from the left and right carbs. I got them petty close to the same and then stuffed it up a bit and stopped because I was concerned of overheating. On returning I connected the home made manometer. Which was once again had the oil sucked out of it on one side as soon as I started it. Right now I think I must blamed the home made manometer, which is 1/4 inch in diameter (too big I think) and about 8 m long with a short piece of 5/32 ID tubing fitted in the pipe which fits perfectly over the pickup. Maybe the larger diameter and then the smaller diameter make it too sensitive to use especially if there is the slightest of imbalance.

    Yes I have done a compression test a time back and it was pretty good. <o:p></o:p>
    #27
  8. bushyb

    bushyb Adventurer

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    Right I did a quick compression check with WOT.<o:p></o:p>
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    Left 140 and right 135<o:p></o:p>
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    The bike has only got 51000km on it. <o:p></o:p>
    #28
  9. _cy_

    _cy_ Long timer

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    got all sorts of manometers, but my favorite balancing tool is a Unisyn. don't let the low cost ($25) fool you. it does an excellent job at low flow and high.

    [​IMG]

    here's a digital dwyer
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    magnehelic
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    here's an unusual one... Wallace & Tiernan Precision Pneumatic Calibrator
    with Series FA-145 Dial Manometer
    [​IMG]
    #29
  10. disston

    disston ShadeTreeExpert

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    Wow!

    Those tools are worth more than my motorcycle. :freaky
    #30
  11. bushyb

    bushyb Adventurer

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    Thanks very interesting. I Googled the Uni-syn and found this.<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:eek:ffice:eek:ffice" /><o:p></o:p>
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    http://www.theminiforum.co.uk/forums/topic/181844-recommend-me-a-carb-balancing-tool/<o:p></o:p>
    #31
  12. supershaft

    supershaft because I can

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    Except that none of them are manometers.
    #32
  13. _cy_

    _cy_ Long timer

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    Uni-syn have been used for balancing multi-carbs for decades. old british sports cars almost all came with side draft carbs.

    the old Stromberg side draft carbs are almost same size/shape of Bings.
    #33
  14. supershaft

    supershaft because I can

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    IMO a properly damped, good manometer can't be beat. They are THE scientific standard. They are in fact Mother Nature showing you what is going on.
    #34
  15. _cy_

    _cy_ Long timer

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    if you had used a Uni-syn much, then you would realize that a Uni-syn is a variable throat size dampened manometer.

    as flow goes across veritable sized opening so one can measure all RPM range. air movement moves a plastic floater, which is dampened by it's own weight. if one wants to know air flow/volume of one carb is higher, lower or same as another carb. Uni-syn will reveal it for any RPM. don't be fooled by Uni-syn's low $25 costs. this is a quality tool that used to be the standard for balancing side draft carbs on old British Sports cars.

    which is exactly how this Bacharach model MZF Draft Gauge works (from my manometers used for HVAC)
    [​IMG]
    #35
  16. supershaft

    supershaft because I can

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    I have used them before. I would much rather use a manometer on our bikes or cars. A Uni-syn is a manometer and a mechanical contraption in one. A manometer itself is neither mechanical or electronic. Therein lies their accuracy and simplicity. Why use a contraption when you can use THE scientific standard that IMO is not only more accurate but easier to use? I am just putting another angle out there for readers to ponder.
    #36
  17. _cy_

    _cy_ Long timer

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    Uni-syn is equally accurate to any conventional manometer. the only mechanical part is throat size opens and closes to compensate for higher or lower air flow for different RPM ranges.

    which brings up a major advantage of Unisyn. it's ability to measure air flow for high and low RPM with same sensitivity. vs a conventional manometer using a wider range, less sensitive meter to cover high and low RPM. so technically Uni-syn is more accurate than a conventional wide range manometer. difference is so small one is splitting hairs...

    draw back to Uni-syn is one cannot mount two like manometers and monitor air flow while riding. now we are splitting more hairs ... as objective is for both carbs to flow same volume of air. which Uni-syn does equally accurate to any conventional manometer with same or less fuss.
    #37
  18. bushyb

    bushyb Adventurer

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    This turned out quite a good topic with a lot of good comments from several experts, ending up discussing manometers!!!!!!!.......<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:eek:ffice:eek:ffice" /><o:p></o:p>
    Well I suppose I could start a new topic.... well let&#8217;s see what the opinions will be as it is related.<o:p></o:p>

    Cable adjustment on throttle and choke.<o:p></o:p>

    I have briefly read a few articles on tuning and adjusting the cables....<o:p></o:p>
    Now this is where it gets difficult to describe and maybe test.<o:p></o:p>
    Let&#8217;s assume the carbs are tuned, balanced, cables adjusted and synchronised etc.<o:p></o:p>
    I believe that there should be some sorts of test or check preformed to confirm your adjustments you have just made are correct other that riding.<o:p></o:p>

    When opening the throttle fully open on the handle bar how do you know that the carb is opening up all the way? Is there a check that can be performed other that using you finger to pull up the throttle lever or cable to check that it is opening all the way up to the maximum or stop lever?<o:p></o:p>

    I would have thought if the pipes from the air filters were disconnected at the time of doing adjustments then you could look in the back end of the carb you would be able to see the opening and closing of the butterfly as the throttle is twisted. (Assuming that going beyond this point would be closing the flow of air???) Once the butterfly reaches the midpoint or the horizontal position in the throat that this would be the fully open throttle position even though there was still room to move the lever or cables more upwards as if to accelerate more. Please give me your thoughts.<o:p></o:p>

    Similarly what would the test be to check adjustment on the choke cable? For example the handle bar lever is moved to the 1/2 choke position. What position must the start valve be in? Also for the fully cocked lever position, how do you check that the start valve is where it is supposed to be? <o:p></o:p>

    So in a nut shell will it make any difference once these cables are set and there is still the possibility that not all the possible movement has not been taken up. <o:p></o:p>
    #38
  19. supershaft

    supershaft because I can

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    Funny. I think they are lot more fuss for a lot less return. I would rather use a plain ol' manometer any day over one. They are less accurate for there super short tube. They aren't more accurate for more or less air rather more or less throttle position but then that is debatable because they measure more throttle but they are flowing the same air as before and not measuring more throttle flowing more air which is really the whole point of more throttle. Closing the throat insures the same amount of air as with the throat more open although the throttle is open more thusly really measuring the same amount of air. A regular manometer measures what is really going on in real time. They can't be beat IMO. If a Uni-syn works better for you more power to it but don't blame the manometer. There are reasons why just about every tuner out there uses a manometer or an electronic gadget that mimics a manometer over Uni-syn's. Whether or not they are connected to the carbs or a flow bench.
    #39
  20. _cy_

    _cy_ Long timer

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    good grief .... talk about beating a dead horse... how many times do you want to discuss the same thing?

    BS a plain manometer is more accurate. they are essentially the same in accuracy, with Unisyn being slightly more for reasons stated above.
    what a std manometer is better at is being able to look at a gauge in a remote location. which is better suited for a tuner because they are running motor, making changes looking for real time feedback.

    a Uni-syn is a tool that measures air flow allowing anyone to quickly balance their carb for dirt cheap ($25)
    don't remember claiming Uni-syn was the best tool for everyone. it's just another tool that works well.
    #40