Carburators

[Merle Coggins]

Not long ago there was a thread (may have been over on the car side) regarding carburators, and one of the posts had a picture of a carb with an aditional adjustment screw in the top. Several asked what it was for, but nobody seemed to know. My carb also had that screw, and since I needed to get into it to fix an accelerator pump problem I figured I'd look into what that extra screw does.

Here's a pic of my carb, showing the screw in question.

I remembered when I went through the carb the first time that there were 2 accelerator pump type of plungers, but I didn't really follow through what they did. In the next 2 pics you can see the 2 plungers and their associated linkage.

Apparently this other plunger is a dash pot to slow down the return to idle. (remember, I have Fluid Drive) The linkage will push it up when the throttle opens and must force it back down into the chamber to return to full idle. The screw adjustment on the top limits how high the plunger lifts, which inturn adjusts how much delay there is in the return to idle. One thing I haven't figured out yet, and I think it's causing me a new problem now that I've played with it, is how it's supposed to damp the movement. I searched and searched for a port to push the cas out of the plunger chamber but found nothing. There is a slot part way down the side that will allow gas from the float bowl to enter the plunger chamber. On the up stroke it will allow gas to be drawn down past the plunger lip to fill the bottom of the chamber. But on the down stroke it seems to take a great deal of pressure to compress the plunger and force the gas back out. It seems that there should be some type of orifice that would let the gas out slowly so that it could act as a damper. After reassembly I now have a problem with it returning to idle. I haven't had a chance to dig into it further. It may just be binding linkage, but I suspect the dash pot damper plunger won't return because the linkage return spring isn't strong enough to push it down into the gas with nowhere to excape.

Has anyone else had experience with this type of carb? Should there be an orifice somewhere to allow the dash pot plunger to work? This is a Ball & Ball DT G1 carb.

Merle