Bing Vacuum physics

[barryh]

The vacuum produced due to increased air velocity through the venturi (Bernoulli's principle) has been explained as the reason for the carb piston lifting. While we are on the theory it's worth considering that the engine is just an air pump and if it doesn't pump enough air through the venturi of a given sized carb, the air velocity achieved may not produce enough vacuum to lift the piston all the way up. The engines abilty to pump air is a function of the differential pressure between the vacuum achieved in the cylinder and atmospheric pressure at the air inlet. Anything that reduces that differential like a restricted filter will affect the engines ability to pump air and sufficient air velocity may not be achieved to lift the piston all the way.

Even without faults you can't assume the pistons will lift all the way up unless the carbs are correctly sized to the engine. So in an extreme example, if you were to put 40mm CV carbs on an R45 the pistons wouldn't even get half way up at full throttle.

So to answer the OP's question a less restrictive air filter would not cause a problem with piston lift. Quite the opposite.

[Major Softie]

WOW! Major Softie needs to work on his bed side manner. I don't need to be hit with the "third grade education" stuff.I know all about Bernoulli's laws......Since Bings are so sensitive I thought the addition or removal of restrictions might throw that balance off enough to bother things. Sorry !!!!

Read it again, and watch for the " ".

The "3rd grade education" comment was not intended to insult, but rather to show how counter-intuitive the situation is. Note that I did not refer to your third grade education, but our third grade educations, and how they run counter to what actually takes place. You may well "know all about Bernoulli's laws," but that did not prevent you from reaching a conclusion/hypothesis that was in direct opposition to those laws. As Barry points out, if a less restrictive air filter was to impact the vacuum in your carbs, the impact would be the exact opposite of the one you were asking about.


If it reads better for you, this was my intent:

By third grade most of us understood enough about what's going on in the physical world to see that air being squeezed in a venturi ought to increase the pressure against that venturi, but some laws of physics run counter to what would otherwise seem obvious.

If you still find it offensive and feel I was telling you things you obviously already knew, may I remind you that I could only respond to the understanding that was evident in your original question, not to things you know all about but didn't apply when asking the question.

[moosehead]

Besides float level.....check diaphragms for rips, tears, leaks?

[dougie]

All of this is why I prefer to not have CV carbs. I know they are smooooooth. But they are mysterious and difficult to mess with if you change the operating environment in which they operate (exhaust, intake, etc.).
I put Mikuni flat slide cards on a Kawasaki 500cc twin that was "built". Every change I made was obvious on a test ride. I did have a rough starting point from the Mikuni manual. A few runs to get the main jet, a few more for the needle, and a little fiddling with air screws.
CV carbs give that nice "driveability" thing, but I only like them on a bike that is stock or close to it. Factory engineers have access to test equipment that we don't when they set up things at the factory.
Bings are great for airheads as most of them have a stock engine, intake, and exhaust.

[Kurt in S.A.]

I like the "driveability" of Bings...they can be good "analog computers" to compensate for changes to atmosphere, such as going up and down in altitude...not the best way to rely on them in the long term, but is very helpful when out touring.

Kurt in S.A.

[Steve in Golden]

Don't panic guys.........I'm putting the air filter back.......I was just looking at things and started to wonder why....................and so on

Damn! Couldn't you have held back on that just a bit longer Tom? There I was, rehearsing an essay in my mind how a vacuum doesn't suck air through the carbs. Rather atmospheric pressure blows the air through the carbs.

Does an airplane fly due to the vacuum on top of the wing sucking the plane into the sky, or the pressure from underneath it blowing it into the sky?

[Duane Ausherman]

Steve asked, "Does an airplane fly due to the vacuum on top of the wing sucking the plane into the sky, or the pressure from underneath it blowing it into the sky?"

You do like to make trouble don't you?

Of course the two are the same, except for perspective.

[Major Softie]

Steve asked, "Does an airplane fly due to the vacuum on top of the wing sucking the plane into the sky, or the pressure from underneath it blowing it into the sky?"

You do like to make trouble don't you?

Of course the two are the same, except for perspective.

Thus, the answer is: yes.

[Major Softie]

I like the "driveability" of Bings...they can be good "analog computers" to compensate for changes to atmosphere, such as going up and down in altitude...not the best way to rely on them in the long term, but is very helpful when out touring.

Kurt in S.A.

As someone who regularly travels from my 6500 foot elevation, up to over 9000, and down to under 100, I like CV's a lot too - and FI even more. I can do all that and back on less than a tank of gas.

[Kurt in S.A.]

Seems to me that the plane lift is a function of the force vectors. If you have a large force vector pushing up on the underside of the wing, and a lesser force vector pushing down on the wing, the net sum of the two vectors is going to be up. In the extreme, if there was indeed a vacuum on the top of the wing, there would be no force vector...can't push or suck. The force vector pushing up therefore is the what moves the aircraft around.

Kurt in S.A.