Can't adjust engine speed down with the carb idle speed screw?
 

About 4 months ago I rebuilt the Aisin carb on my '86 pickup. Went pretty smooth, mounted it back on the intake and it ran pretty well. Well enough that I just drove it that way for 4 months. I was having a cold start issue, which I figured out yesterday (spring inside the choke housing wasn't wound up enough) and little bit of a backfire going down hill with engine braking.

So I figured that it was time that I finally get this thing tuned up correctly. I'm trying to do the old method of adjusting the air/fuel to max rpm and then adjust down with the idle speed screw. I've got the idle up to 1300 rpm by adjusting the air/fuel screw, but I can back out the idle speed screw all the way without a drop in rpm. I can adjust the idle up by screwing in the idle speed screw.

I have the float adjusted to keep the fuel level at the lower part of the looking glass as I was told that it would help prevent stalling offroad. Could this be part of the issue? Any other ideas? Thanks!

Well, after a few more hours, I think that it was the float. I readjusted the float and now everything seems to adjust as it's supposed to.