Graphic of how CV carbs function

[chuck hahn]

Someone needs to get ahold of a MOD and get this made a STICKY.

https://www.facebook.com/interestingengineering/videos/1574395025963529/

Youtube link.....not the best video seeing i was taping off the computer screen but you get the idea. Note that oue GS carbs have the mixture screws on top but its the same thing

https://www.youtube.com/watch?v=JS34TkkeYdo&feature=youtu.be

 

[Guest]

Very cool, but I'm not sure if it can be seen without a Facebook account.

 

[chuck hahn]

Im uploading now to Youtube and will be posting a link shortly...stand by.

 

[chuck hahn]

Youtube link added to post #1

 

[Wingsconsin]

Deleted in favor of the post below

 

[Rijko]

cool. found the original movie :

 

[gordinho80]

Was able to save the video to my desktop and upload it directly to YouTube

https://www.youtube.com/watch?v=5bYRk9OoR6U

 

[Steve]

Nice video, but it's blatantly WRONG about how the vacuum lifts the slide. :-k

They show ported manifold vacuum lifting the slide. Maybe on some other carbs, but NOT on a GS.
In that situation, when the throttle is just barely opened, the vacuum port will be exposed to manifold vacuum, which should lift the slide almost instantly. As more throttle is applied, manifold vacuum will drop to near ZERO, which would have the slides slamming shut, right when you need them open, at full throttle.

The vacuum that lifts the slides comes from the air rushing UNDER the slide, through the venturi. The hole on the bottom of the slide 'reads' that vacuum and ports it to the chamber above the diaphragm, THAT is what lifts the slides. It is not directly related to throttle position, it is related to the velocity of air through the venturi. Yes, that will be controlled by the throttle, but not directly.

I see that the original movie has been found, but I was able to see the Farcebook version, I do NOT have an account. :encouragement:

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[Gorminrider]

(haha good catch Steve YUP that don't look like this...)

 

[850 Combat]

(haha good catch Steve YUP that don't look like this...)
View attachment 53114

This is a cut from the factory manual. That section goes on to show more detail including which ait jet is which, and schematic data which allows you to easily figure out where carb cleaner should be coming out if you spray it into any of the orifices. This allowed me to find and fix a clogged air passage which was not cleaned by a soak on a 1000G. It is found in the high resolution GS850G manual on Cliff's site. It can be hard to find there, as the file is so large.

Super useful information

 

[chuck hahn]

Its just a BASIC explanation guys....unknot your undies.

 

[Steve]

Yeah, but even BASIC should be CORRECT. :-\\\

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[chuck hahn]

On some models im sure it is correct..maybe not a 80s Zookey but its correct for some bike somewhere.

 

[chuck hahn]

maybe there is a difference between CONSTANT VELOCITY and CONSTANT VENTURI. Ive seen both mentioned in service manuals. havent personally investigated difference between the two representations...or if there is ant differences at all.

 

[Steve]

A "constant velocity" is obtained with a VARIABLE venturi. The slide is what makes it variable.

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