Adjusting the Idle Mixture on CV Carbs

[Steve]

Here's some food for thought, I've had a few viruses in the past, and the hardest ones I've found to eliminate, were the ones that actually infected the virus protection software itself, which why I would never use Mcafee again, ... Try using another virus software from a disk to scan your system to include the virus protection program.

Thanks, I don't use McAfee, either, but for other reasons. :-\\\

I have had an offer provided to me to use another system, will have to wait until I get home in a few days.

The "infected" file is a system file. I am going to load an "upgrade" to Windoze, maybe that will overwrite the file. If not, I wll be cashing in on the offer for the other software.

.

 

[koolaid_kid]

Steve, have you tried MalwareBytes?
It is free, and I use it on client's machines. It is constantly updated, so I always download a fresh copy when I go do some work.

 

[Guest]

Thanks for the write up.

 

[koolaid_kid]

You are welcome. I asked Cliff to post a PDF on his site. Just sent him a copy.

 

[rustybronco]

Steve, You once posted you had your virus warning go off on you on a picture I had posted on imageshack that wasn't infected. As George suggested try malwarebytes and I also might add try safer-networking's spybot search and destroy and superantispyware portable. Those are a couple of other good products to scan with as well.

 

[GateKeeper]

Get Microsoft DART and fix your problem....

just a thought

.

 

[koolaid_kid]

Gentle bump to get to the forefront until Cliff has the time to post on his site.

 

[loud et]

Gentle bump to get to the forefront until Cliff has the time to post on his site.

Been reading your new adjustment thread. I appreciate the simple format for my simple mind. I get confused easily.
If you could explain a bit of CV carb function theory to me now.
According to your first post:

"Richen the mixture - rotate the pilot air/fuel screw counter-clockwise
Lean out the mixture - rotate the pilot air/fuel screw clockwise."

What is actually happening when the mixture screw is turned? You obviously know the tiny hole that the mixture screw will poke through in the carb throat if it is lightly seated.....is that tiny little hole actually the one that is allowing more air in/blocking more air, that changes everything?
Before I thought backing the screw out would allow more air in, making it leaner. But now I know out means richer, therefore the increased airflow must actually " vaccuum" up more fuel into the mix?....
and on the exact flip side , my former thinking thought tuning the screw in would block more air, making it richer, but if I understand correctly now, it cuts the airflow down, somehow "vaccuuming/drawing" less fuel into the mix?

I must assume there is another hole down in the mixture screw shaft that I have never noticed. If the tiny hole in the carb throat(where I mentioned the mix screw will poke through) does in fact let more air/vacuum/or pressure in, this other hole in the vertical shaft where the mix screw is inserted, is the opening that is affected. The hole that receives more pressure or vacuum which in turn affects the increase or decrease of fuel delivery?
I am just talking out loud here trying to explain myself. I know that was probably confusing. Id rather ask and understand than be ignorant.
Where/how does the actual CV mixture screw magic happen?

 

[koolaid_kid]

O.K., you asked for it. In order to fully understand what is going on, you have to understand the entire pilot circuit. This is taken directly from the web:

PILOT CIRCUIT

This is sometimes called the "idle circuit" but it does a lot more than control idle. And it is perhaps the most misunderstood of the three circuits. The role of the pilot circuit is basically to run the engine when the throttle is closed, as when the engine is idling or the throttle is closed on deceleration. But this circuit is also the main source of fuel at very small throttle openings. As the throttle is opened past 1/4, the importance of this circuit diminishes, as the main fuel supply is now provided through the main "fuel hole" and controlled by the needle/needle jet and ultimately the main jet. But the pilot circuit does remain active and makes a (progressivley smaller) contribution all the way to WOT.

The typical set up is this: The pilot circuit get its fuel from the float bowl through the pilot jet. The circuit also has a pilot air jet, but the purpose here is not to provide all the needed air (as in the starting circuit), but to provide air to premix with and partially aerate the fuel before the mixture enters bore and completes the atomization process with air traveling through the bore. Such little air passages are sometimes called "air bleed" circuits.

This circuit typically has two outlets. One is called the "pilot outlet" and is located on the engine side of the butterfly valve. This outlet supplies the fuel mixture to support idling and deceleration (that is, off-throttle running). It has an adjustment screw which controls the amount of fuel mixture entering the bore under off-throttle conditions. This screw is sometimes mistaken for an "air screw" but it is not. Turning in (right) reduces the amount of fuel mixture, and turning out (left) increases it. In for lean, out for rich.

The other outlet is call the "bypass outlet" and is located right at the point in the bore where the bottom of the butterfly comes to rest when closed. Typically, the butterfly is set a tad open to permit just a slight amount of air to pass by at the bottom to support idle and decel, and most of the fuel for these functions is supplied through the pilot outlet. But as the butterfly is opened, more air flows past it, and the venturi effect starts to work on the bypass Additional fuel is now drawn out of the bypass to support low speed running and cruising at small throttle openings. (Note that if the butterfly valve is adjusted to 'fully closed' the engine will probably not start or idle. It needs to be open a tad. As mentioned above, these outlets continue "giving" throughout the rev range, but their contribution to the overall mixture diminishes as the slide rises.)

Digest this a bit at a time. It will come to you as it sinks in.

 

[loud et]

you: Digest this a bit at a time. It will come to you as it sinks in.
me: agree.

Thanks for your effort and response. I am starting to see the relation betweeen the mix screw and the idle circuit , as the article said "the holes on the engine side of the butterflies"
Certainly takes time to grasp the whole thing. I have done good rebuilding carbs and getting the gs's to run, trying to make it less guesswork and more calculated adjustments. thx.
I blued a set of pipes and dont want to make these miscalculations again.
It is so true, a bike that runs like crap is just worthless and unenjoyable.

 

[Guest]

Very enlightening... thanks again George!

 

[koolaid_kid]

We exist only to serve. (LMK if you know the book that quote came from.)

 

[BigD_83]

We exist only to serve. (LMK if you know the book that quote came from.)

My first thought was an Aasimov story,but now I'm thinking something much drier...and set more in an apocalyptic future/parallel universe...wink me a blue eye if I'm close

 

[koolaid_kid]

Wink wink

 

[Frank Z.]

Great info, KK. Thanks!
Just added to my subscribed links

 

[john82q]

KK great info,
JUst a suggestion, how about combining some how it works theory into the indroduction for your procedure?

And a picture for the "Visual Learners"

This picture from the manual is a good start, but it would be great if someone with the image manipulation/creation skills and time, could make one in colour without the cross hatching so its clearer.

oh and I like Mr Herberts work too...

 

[loud et]

You are right John 82. Chuck H had put up a carb theory article that was a good read but long and I got bored. IIRC it was not CV's either but general carb theory.
After seeing your post above I recalled this info is in the service manual, which it looks like you may have used for your reference.
Anyways, thank you all.

 

[koolaid_kid]

As I indicated in my post, I found a web page and filtered through all the extraneous crap and just gleaned what answered loud_et's question. It may have been the same stuff that Chuck H had posted, because it did have a lot of general carb theory, which was not germane to the request.
It would be more appropriate in the Appendix. That way, someone who just wanted to get the mixture screws set correctly can do it quickly and easily and not hurt their brain. Those more interested in the theory could dig into the Appendix to understand it.
I have no image manipulation skills, so someone else would have to do that work.

 

[Gorminrider]

Thanks,old_skool. The ol' gs400E Im tinkering with has "hanging idle" throttle and this will get to the "things todo first and in order" really quick and concise.

 

[Guest]

Just subscribing to the thread to read later. Good info.