What is this carburetor adjustment screw?

[velvetfoot]

It's on a carb for an older chipper that's not running for another reason, I think.
I thought it was for draining the bowl when I was putting it away last year, but apparently not, and I'm not sure what it does.
It has a spring on the outside and has a needle-like appearance when removed.
The air comes in from the side.
Thanks.

 

[Ashful]

There are 16 screws in your photo. Care to tell us to which one you are referring?

 

[Jags]

Of the 3 spring loaded adjustment screws (on the carb) in your pic...
The top is the idle adjustment. The one slightly lower and to the right is the air adjustment and the one on the bottom left of the bowl is the fuel jet adjustment.

 

[velvetfoot]

I thought it was for draining the bowl when I was putting it away last year

The screw at bowl bottom

 

[velvetfoot]

Of the 3 spring loaded adjustment screws (on the carb) in your pic...
The top is the idle adjustment. The one slightly lower and to the right is the air adjustment and the one on the bottom left of the bowl is the fuel jet adjustment.

Thanks much.

I got it running, though that screw wasn't why-needed priming-was on unlevel ground. I discovered that it wouldn't run with the screw all the way in, so I backed it out some until it runs. The fuel jet screw was the only one I messed with.

 

[duramaxman05]

The screw with the spring on the bottom of the carb is the high idle fuel/air mixture screw. The one in the picture that is top right is air/fuel mixture at idle