Carb issues

[chuck hahn]

Thanks...I had not seen that pic before. Is that from your service manual??

[chuck hahn]

So basically what i have read and the way I have understood it is reverse? the kidney bean shaped area is actually supplying the equalization air for the bottom of the diaprams so the vacuum can suck them up..right???

[JTGS850GL]

Now you have it right. The hole (number 6 in the diagram above) is exactly the one that I was referring to. That's the hole that supplies vacuum to the top side of the diaphragm through the slide. It's the passage that is enlarged when using the DJ stage 3 kit. The large opening at the front of the carb supplies atmospheric reference to the area below the diaphragm. There's also a smaller passage that leads from the area below the diaphragm to the throat (engine side) of the venturi path and another that feeds the air to the starter circuit. Not exactly sure what the purpose of the passage that leads back to the venturi does. Maybe used to meter the response of the slide.

[tom203]

Thanks...I had not seen that pic before. Is that from your service manual??

Service manual? I don't need no such thing- I got the gsresources! Hopefully the internet stays on.

[JTGS850GL]

Just for completeness, I took another look at that drilled passage that comes from the area under the diaphragm and into the area between the engine and the throttle plate. Seems like it's the passage used for the starter circuit. Air enters the passage through the oval shaped opening at the front of the carb. It then moves to the drilled passage under the diaphragm. When the start circuit path is opened the air moves down through that passage and then is mixed with fuel as the plunger is pulled out. The air/fuel mixture then exits into the venturi passage AFTER the throttle plate. Now it makes sense why opening the throttle, when you have the choke on, screws up the mixture.

[tom203]

Just for completeness, ?.." Now it makes sense why opening the throttle, when you have the choke on, screws up the mixture.

Sure does, mine falls flat on its face! Thanks for explanation- this just might make those got-to-have pods guys think twice

[chuck hahn]

I always had thought them hole in the slide was for transferring air from one side to the other so they would fall smoother and quicker. VMs are mechanically linked and the hole in them allows air to go from below to top for what I think is this very reason.

Then I read threads here about drilling the holes larger so they fall and react even quicker.

[JTGS850GL]

It makes sense if you think of the hole as a fluid transfer conduit. The larger the hole the more volume of air that can move through it. This would make the slides react quicker because the pressure change would occur faster. Faster in, faster out means quicker response in both directions.