cvk34 vulcan 500 carb problem

Discussion in 'Motorbike Technical Discussion' started by matt.trenholm, Nov 4, 2006.

  1. Erm?
    The Older Gentleman, Nov 7, 2006
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  2. matt.trenholm

    B-12 Guest

    Name your exception. I know you're going to.

    Vacuum doesn't lift an airplane's wing, it's the differential pressure
    between top and bottom, and the reaction force of the downwash.

    Some classic lab demonstrations:

    Take a rubber suction cup and wet it for a good seal and stick it onto
    a piece of glass.

    You can pick the glass up with the suction cup because of the weight of
    the atmosphere,
    over a ton per square foot, pushing the outside of the rubber cup
    against the glass, not because of vacuum inside the cup.

    Place a piece of cardboard over the top of a full glass of water and
    quickly invert the glass, while holding the cardboard against the top
    of the glass. After a certain amount of water leaks out, a low pressure
    empty area will form in the bottom of the glass, which is now on top,
    and you can take your hand off the cardboard and atmospheric pressure
    (over a ton per square foot), will hold the cardboard against the rim
    of the glass.

    A physicist once took a pair of metal hemispheres and placed the lips
    of the hemispheres together and evacuated all the air from the
    hemispheres which were now held together only by the weight of the
    earth's atmosphere (over a ton per square foot).

    Two horse pulling on the hemispheres in opposite directions could not
    separate them...

    Take a wooden spool from your wife's sewing box. Push a pin through a
    small piece of cardboard and put the pin into one end of the spool and
    blow air through the other end.
    The harder you blow, the harder the weight of the atmosphere (over a
    ton per square foot) will push the cardboard against the spool.
    B-12, Nov 7, 2006
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  3. No vacuum, no effect of air pressure.

    Can't have one without t'other.

    Action and reaction (after a fashion). So you can as validly say that
    the vacuum is holding them together as you can say that air pressure is.

    Got any more thoughts about car-type bike clutches, while we're at it?

    Look, let's be honest here. You know a lot. There are also some amazing
    gaps in your knowledge and a lot of perceived wisdom and bias
    masquerading as fact (like when you said chain oilers are a waste of

    However, as I've said many times, if you say something on Usenet that is
    manifest bollocks, and get called out over it, it's a really good idea
    to shrug, fess up, say "I goofed", or similar, and everyone moves on.

    Moving goalposts, inventing "reasons" and "you're saying xyz, then?"
    excuses makes you look an imbecile and, and puts you in the same
    category.... Hoyt McKagen, who was another bod who knew a lot but couldn't
    remove the blinkers when necessary.
    The Older Gentleman, Nov 7, 2006
  4. matt.trenholm

    B-12 Guest

    B-12, Nov 7, 2006
  5. OK, let's have the reasoning. Without a vacuum, the air pressure would
    not hold them together. Yes, the air pressure is pressing the parts
    together, but without the vacuum....

    und so weiter, und so weiter, ad nauseam.

    The two are inseparable. Yin and yang, equal and opposite.

    It's semantics anyway - people talk about vacuum gauges, vacuum taps,
    vacuum cleaners and vacuum forming, for a pretty good reason.

    Now, got any more thoughts on car-type dry clutches?
    The Older Gentleman, Nov 7, 2006
  6. matt.trenholm

    oldgeezer Guest

    B-12 schreef:
    Yes, bollocks.

    Vacuum does not suck, The differential pressure pushes.
    At least that is what I was tought when I studied aircraft design.
    But it doesn't really matter what you say, as long as the result is
    the same.
    It sometimes is easier to calculate how much (mass/second) air is
    pushed (accelerated) downwards by a wing than to calculate
    the pressure at each square mm of the upper (curved) side
    and the lower (curved) side of a wing and multiply that by the
    surfaces of upper and lower wing side, corrected for the angle
    of each square mm to the vertical, in order to get how much lift
    this wing gives.
    Done properly, both calculations give the same result.
    So in effect you also may say that acceleration of air downwards
    is what the wing tilts upwards. There is action=reaction for you.

    I used to read this NG regularly many years ago (at work), and
    only recently rediscovered it. What has happened to the famous

    oldgeezer, Nov 7, 2006
  7. This is more or less what I've said in my posting made a couple of
    minutes ago. Yes, the air pressure pushes things together, no it
    wouldn't without a vacuum, yes, it's semantics.

    As for Hoyt, he dropped off the twig a year or so back.
    The Older Gentleman, Nov 7, 2006
  8. matt.trenholm

    B-12 Guest

    Newtownian physics is about force and mass and time. Pressure is a
    force. Vacuum is the opposite of that force only because the force has
    been removed.

    Back to my nap...
    B-12, Nov 8, 2006
  9. Hence my qualification "(after a fashion)." Which, I note, you have
    deliberately chosen to ignore.

    Look, I'm not disagreeing it's about pressure differential. Merely that
    it is so much easier to go along with everyday terminology. See my brief
    explanation of how a Kawasaki 550 fuel tap works, elsewhere.

    There is just no need to complicate things. KISS. I mean, wlesewhere
    some bloke is asking for a simple home job to improve his XT350 front
    forks and you give him 5000 words of tech bollocks. Why?
    The Older Gentleman, Nov 8, 2006
  10. matt.trenholm

    GaZ Guest

    This will not assist the original poster who is probably looking for a cure
    not quotations from engineering reference books. If you understand the
    principle, the terms are irrelevant.

    If not, the same applies in this case.

    I defer
    GaZ, Nov 8, 2006
  11. GaZ wrote:

    Precisely. "Pressure differential" was the phrase I was struggling for
    (thanks to the bod who supplied it).

    If someone wants a fix, they want a fix and not reams of irrelevance.
    chateau.murray, Nov 8, 2006
  12. matt.trenholm

    B-12 Guest

    Don't forget that you're the one who directed the thread off into these
    thorny bushes with your diaphragm that magically detaches and
    reassembles itself to the slide.

    What the heck year and model had diaphragms that weren't securely
    fastened to the slide, some 1968 Honda CB350?

    The OP has a more modern machine than that, and the diaphragm will be
    fastened to the slide with a plastic ring.
    B-12, Nov 8, 2006

  13. Or bonded to it and not separable. Never seen a replaceable diaphragm
    on any Jap bike, although IIRC BMW Bing diaphragms are available as
    separate units.

    The place for replacement diaphragms, if anyone is ever interested, is
    NRP Carburettors, here in the UK. Send them your old diaphragm/slide
    assemblies, and in a week or less they attach new diaphragms and post
    them back (might take a few days longer to the US).

    Incredibly good product, costs a third to a half the price of OE, and
    excellent service.
    chateau.murray, Nov 8, 2006
  14. matt.trenholm

    GaZ Guest

    What the heck year and model had diaphragms that weren't securely

    1996 Virago, close relitive of the bike in question.

    The diaphragm is attached to the slide by 'sandwiching' the centre cut out
    rim between a cylindrical sleeve and the inside of the slide. When the
    diaphragm lifts the sleeve, the slide does lift with it. When the diaphragm
    returns under the spring force, it re-inserts itself and looks ok to a
    casual inspection. It was only spotted by looking down the carb while the
    bike was running.
    GaZ, Nov 8, 2006
  15. matt.trenholm

    B-12 Guest

    The original equipment carbs on my GSXR have that cylindrical sleeve
    you mentioned.

    It's made of ABS plastic, like the slides, and there are four plastic
    pins extending from the cylinder, through holes in the slide, and the
    ends of the pins were heat formed into plastic "rivet heads" so the
    parts couldn't come apart without breaking something.

    I would think that Hitachi (or whoever made your Virago's carbs would
    at least superglue the cylinder into the slide.
    B-12, Nov 9, 2006
  16. matt.trenholm

    GaZ Guest

    The bike was almost 4 years old when I got it, so it is possible that the
    diaphragms were replaced by an aftermarket 'fix'.

    I know it is not a likely problem, but I thought I would mention it as it
    took me a while to find as I had never seen or read of it before.
    GaZ, Nov 9, 2006
  17. matt.trenholm

    B-12 Guest

    Perhaps this will open a whole new dialogue into "Loose Diaphragm
    Syndrome" and how it defeats the aspirations of new riders. ;-)

    Oddball mechanical or electrical problems become grist for the
    experienced mechanic to
    talk about---or even start a small business dealing with the rare

    One oldtimer at the RC airfield had a problem with fuel starvation on
    one of his ARF's.

    So he started his own cottage industry right there on the picnic table
    at the RC field.

    He would tell newbie RC pilots that the fuel starvation problem was
    very common, and he would charge them $20 to cut the top of the
    fuselage off their brand new $500 ARFand convert it into a removable
    fuel tank access hatch...
    B-12, Nov 9, 2006
  18. matt.trenholm

    GaZ Guest

    Without intending to drag off subject again, I am hardly a new rider. My
    first matchless in 1962 was followed by around 60 other assorted specimens,
    and 4 years of my apprenticeship was spent in a Honda dealer.

    But I am of the opinion that no matter how oblique a cause is, it is easier
    to find if others have mentioned it.

    And. as in the old saying, in the land of the blind the one eyed man is
    GaZ, Nov 9, 2006
  19. matt.trenholm

    B-12 Guest

    As I recall, it was H. G. Wells who exploded that particular myth. His
    protagonist went into the Valley of the Blind in South America, and the
    peasants poked both his eyes out in order to make him "normal".
    B-12, Nov 9, 2006
  20. Quite the conversation guys. Sorry I havent posted in so long, to be
    honest I am just about fed up with this &*$&ing bike. I have to store
    it at my parent's for the winter, except they live 2 hours away so time
    is ticking before the snow starts flying. I guess Im just so fed up I
    dont want to bother with it anymore.

    But today I went at it again.

    So, GaZ, you were mentioning that the slide was seperate from the

    Okay. That's not it though, the diaphrams seemto be intact and seated
    properly. One was a bit off, but popping it into itself let me seat it

    The problem remains; the throttle cuts out the engine when it is

    I once again hauled it apart and cleaned the three little holes goingto
    the pilot circuit. To whomever asked if I accidentally put the pilot
    and main into the wrong areas, I didn't :) I've changed the plugs again
    to be sure they arent the culprit; someone on anther forum said, while
    the possibility was quite remote, that the new plugs I put in were from
    a bad batch.

    So I dont know what to tell you guys. I dont know why a) something
    would be this plugged up if it worked before I cleaned it, I understand
    some sediment might have came loose but this is ridiculous and b) why
    both carbs are affected. As someone else said, you would think that one
    cylinder would be working correctly.

    Which leaves me to believe that I have overlooked something stupid, and
    this stupid thing is affecting both carbs. I've double checked the
    parts diagram eleventy billion times. And I did make sure I put the
    needle jet in the correct way. My needles are not bent at all, they are
    perfectly straight. They are also in the right way ;)

    I'm going to play with the floats tonight to try to get them spot on; I
    personally dont think thats the problem because I didnt touch them when
    it was disassembled but who knows,I may have bent them both a little
    with all this man handling.

    Believe me your continued suggestions, no matter how stupid they are,
    are well appreciated. As I've said, I figure its something REALLY
    stupid and something that is mutual to both carbs that is keeping
    these things from working right.

    Thank you so much.
    matt.trenholm, Nov 10, 2006
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