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pilot air screws

This is a discussion on pilot air screws within the ZX-12R forums, part of the Kawasaki Motorcycles category; Dispute this biotch! From Factory pro on TUNING CVK CARB!!! 4. Idle and low rpm cruise Fuel Screw setting (AKA mixture screws) There is usually ...


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Old 02-16-2013, 10:40 AM   #16
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Dispute this biotch!

From Factory pro on TUNING CVK CARB!!!

Quote:
4. Idle and low rpm cruise

Fuel Screw setting (AKA mixture screws)
There is usually a machined brass or aluminum cap over the fuel screws on all but newer Honda. It's about the diameter of a pencil. Cap removal details. Newer Honda carbs have no caps, but use a special "D" shaped driver, usually supplied in the carb recal kit. We do have them available separately, too. 800 869-0497 to order -
Set for smoothest idle and 2nd gear, 4k rpm, steady state cruise operation. Set mixture screws at recommended settings, as a starting point. For smoothest idle, 2nd gear 4000 rpm steady state cruise , and 1/8 throttle high rpm operation. (pj tuning information)
Pilot fuel mixture screw settings, float level (but, you've "fixed" the fuel level in Step 3 - which you have already done!) AND pilot jet size are the primary sources of mixture delivery during 4000 rpm steady state cruise operation.
If lean surging is encountered, richen mixture screws (turn out) in 1/2 turn increments. Alternative pilot jets are supplied when normally required.
Pilot fuel mixture screw settings, float level and pilot jet size also affect high-rpm, 0 to 1/8 throttle maneuvers. Too lean, will cause surging problems when the engine is operated at high rpm at small throttle openings! Opening the mixture screws and/or increasing pilot jet size will usually cure the problem.
NOTE: A rich problem gets worse as the engine heats up.
If the throttle is lightly "blipped" at idle, and the rpm drops below the set idle speed, then rises up to the set idle speed, the low speed mixture screws are probably set too rich: try 1/2 turn in, to lean the idle mixture.
NOTE: A lean problem gets better as the engine heats up.
If the throttle is lightly "blipped" at idle, and the rpm "hangs up" before dropping to the set idle speed, and there are no intake leaks and the idle speed is set at less than 1000 rpm, the mixture screws are probably too lean: try 1/2 turn out, to richen mixture. Be sure there are no intake leaks and the idle speed is set at less than 1000 rpm!

Again turning them OUT richen the damn low speed pilot circuit! CVK 36 and 40s have the pilot screw FORWARD of the float bowl.

Last edited by beantown; 02-16-2013 at 10:44 AM.
   
 
Old 02-16-2013, 11:04 AM   #17
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Old 02-16-2013, 11:26 AM   #18
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According to this diagram...that's your idle screw. Idle screw controls air/fuel ratio at idle. Your jet controls fuel flow rate, hence why Keihin sells alternative jets with ALL of their tuning kits. Got that right from their NA site. Perhaps I shall look at the Japanese site as well...but I don't speak nor read Japanese so....

Now, if you look closely, the reason they are saying it "richens" the mix, is both air and fuel are traveling down the passageway in the carb body. Look where the air inlet is. Air travels past the pilot jet, where it picks up fuel vapor, and this all passes out the tiny hole in the carb that controls your idle.

I see what you are saying now.
   
 
Old 02-16-2013, 03:06 PM   #19
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Pilot Air Jet (not shown) ~ Follow that boss like air tunnel from the air cleaner side to the 'pilot mixture screw.'

Did I say fuel is the engine side? So turn the 'pilot air screw' in and no air comes out the tunnel = Rich.
Did I say air on the air cleaner side is going to be the screw that closes the atomization like the engine side? = Rich.

If your nose is not clogged, I set a vacuum cleaner over your two openings, will I suck air out of both or one side of your nose? If I WOT the air sucking for all its worth, we do what? The one orifice closes? How can you shutdown an open hole without a spider's trapdoor there.

You bring in some jacknose netshit printed up what? You want me to believe anything this guy says?: "Pilot fuel mixture screw settings, float level and pilot jet size also affect high-rpm, 0 to 1/8 throttle maneuvers." The main is part of idle and starting. The low speeds blend in at such a linear move, you can't even tell that the whole system is being sucked out in proportion, from the start of that 1 degree move to WOT are you smoking, fella?

Nice try

Dude, you bring in shit to quote, you can't walk it. Even that abstract has holes (pun intended) like swiss cheeze IS! 0 to 1/8th my ass crack is so linear too, ya think?!
   
 
Old 02-16-2013, 03:24 PM   #20
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Goddamit! I smell danish!!

Tell me where! I WILL possess the danish!!
   
 
Old 02-16-2013, 03:35 PM   #21
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From: Pure Bred Minnestrohtan
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I said I see what he is saying....

There is no air screw per-say. It is an inlet that grabs fuel on the way by from the pilot jet. It's an air jet. You control fuel rate with the pilot jet. You control the entire mix with the idle mix screw.

Or so it appears in the pic I used there...looking at the flow channels in that there carb body.

I know what you are saying...

When you open the throttle, it pretty much cancels out this "jet". Same principle some have explained here with the power commander to eliminate the backfire on decel by richening up the 0 throttle range at high RPM. The same is what he is saying with that screw...or so I understand anyways...

Eh...fuck it.
   
 
Old 02-16-2013, 04:38 PM   #22
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Old 02-16-2013, 06:47 PM   #23
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From: CA
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Quote:
There is no air screw per-say.
Disagree. We haven't lost that screw since the Linkert or before that carb design. We have air screws on FI throttle bodies. I believe they (air screws) are forever?

Quote:
When you open the throttle, it pretty much cancels out this "jet".
When I throw the fan switch to high, does one of your nostrils cancel out? Nope. Will it cancel out a jet hole? You need to show it to me; is that spider door you be knocking on is that symbol on my gas tank.

Quote:
Same principle some have explained here with the power commander to eliminate the backfire on decel by richening up the 0 throttle range at high RPM. The same is what he is saying with that screw...or so I understand anyways...
Don't bring in the pc or I'll bring in PAIR and we have yet to put my video together with the popping, the AFR meter reading leaner: with me coming up with the faster way of turning/tuning the air screws I meguyveered in the video... Once again, connect the dots.

Quote:
Eh...fuck it.
I would have quit long ago, but to get booted off sites, it's always been aboutechilarity. Look, solid-liquid-gas. Lets eliminate the air in a glass. Lets put a solid in there so you can see ratio.

Lets try this one more time The penultimate number is that liquid filled to the brim no matter how many rocks in the glass vs. water = AFR.

The penultimate number that enters the cylinder chamber is 14.7 minus a ratio say, so it does not confuse you. Now, we toss a rock into the glass and that displaces what was once water (air) so now that rock takes up a ratio.

The 14.7 pressure did not change. It's going to compress the water and rock together. As if you could compress the water and rock in the glass, go ahead, I'll watch. So, did you destroy or create 14.7 is there is no change, you grasp that concept.

Now, add an air screw in the mix. I want air to tumble into the gas and break it up. I do not want a solid steam out the end of my penisay If I have to use nature for the subject, hello?

Now that you have that image, we piss thru a straw with holes all up that tube. Did I disrupt the solid stream? Yes. So if I could get someone to suck on that straw, change direction meaning, we'd catch air in those straw holes as someone be drinking the acid flow out the bladder, or petcock say

We turn the screw out, we add more air that moves faster into the straw holes, rather than a heavy liquid stream trying to squeeze thru a tiny hole. So the air wins being sucked out faster/sooner than gas entering the [closing pressure] of 14.7.

Notice the new fuel to air ratio a screw makes. You can't measure it, but you sure can see it move, if you used an ohm meter hooked up to the, 'stator rotor movement,' meaning, out those wires if you bumped it under 1 degree. Fascinating to watch. After all, WATTS the difference in either movement?

Last edited by hubz14; 02-16-2013 at 06:56 PM.
   
 
Old 02-17-2013, 06:41 AM   #24
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From: Sussex England.
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It's not an air screw it's a mixture screw.

Screwing the mixture screw out doesn't add more air moving faster into the straw holes, mixing with your piss, undoing the screw allows more air/fuel mixture to be drawn past the taper into the cylinder.

More air/fuel mixture means the mixture is richer.

No glass, no rocks, no water, no straw, piss acid or anything else.
   
 
Old 02-17-2013, 09:20 AM   #25
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From: CA
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Quote:
It's not an air screw it's a mixture screw.
I'll have to disagree/agree. Yes, obviously it's a mix. Follow my thinking. If I have an air screw on the FI throttle body, it is obviously an air screw. Like I said, that screw is forever. There are no fuel tunnels in a throttle body. The injector is it as far as fuel entry or a passageway. And it sure does not atomize if it's closed or open, correct? But there sure are air tunnels for the IAP and air screw setting still.

So when I run the air screws in, there is more gas that displaced what that screw would have with air. If opened at who cares the position, right?; It will offset the AFR from start to WOT down the salt flats is the overall tune, correct? And now you read your spark plug: chop the engine spark iwith a WOT, look down the porcelain with the proper toolookey there!

The question is, who is displacing whom, we turn something hooked up to a tunnel of air? Am I mixing air in the throttle body? Yes. There is nothing going thru those tunnels but air. So too is the air hole closer to the intake valve. So the fuel is going to spittle back into the throttle plate and wait for the next round. That says the air screw is going to enter before the fuel and equalize that close to the penultimate. That tiny spit out the close is just that. Balanced is the constant. OfF is the AFR and that ratio by that screw turn.


Make sense doughnuts to danishes about air and calling it an air screw? You could say we stole the 'mixture' screw off the carb. Stuck it on this new animal. We now use it for engine balance like we should have when the first inline with 4 carbs came on line. Same as the 1's and 0 so late in the game.
   
 
Old 02-19-2013, 06:38 AM   #26
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From: Pure Bred Minnestrohtan
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There is fuel coming out of this needle. The pilot jet feeds out at this point in the bore...or so I can clearly see in the above referenced image I posted. Without the carb body in my hand, I can't really say otherwise, but the cast-in channels show this to be the case here.

This supports the "richer" mix when it's backed out. It is adding more fuel. Air is also passing via this as well, hence "mixture". The air jet is open at the intake of the bore, no needle there.

Now, the pilot jet looks as tho it can also go another direction in there as well. Again, without the carb in my hand, I can't be certain, but I do see, with this pic, what is being said. Whether or not that pilot jet is feeding another passageway....seems it's going multiple paths there. Either way, it's clear fuel is passing with air via the 1 passageway anyways, as the air jet path passes right thru the pilot jet hole.
   
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