Small Engines (Lawn Mowers, etc.): Carburetor adjustment, coleman generator, needle valve

Question
I have an older Coleman generator that belonged to my father. It sat up for years, but he did drain the gas out of it before he stored it. I am trying to get her up and running, but I am having a difficult time adjusting the carb properly. I think the carb is a 390323. It has a 8HP B&S motor - 190432-3070. I got it running, but the motor surges. There is a storm coming and I would like to get this straightened out tomorrow if possible. Now, to the problem...

I can turn the needle valve all the way in and it will try to die. If I let it out some, it idles better but surges. It doesn't matter what I do to the idle valve, it makes no difference in the idle. When I first start it, I have to run it for quite a while with the choke (choke-a-matic?)closed before it will idle on it's own. I have seen several diagrams showing an idle speed adjusting screw, but I can't figure out for the life of me how that affects the idle. Thanks in advance for your help.

Answer
That idle screw is a low idle mixture screw and only effects he engine at a low idle. That is set with the throttle set at a low idle. I feel your needing a carb rebuild. The cause of 90% of all small engine problems. After rebuild before putting the carb back on set the main at 1 1/2 turns out, and the low idle screw at 1 turn out for your initial settings.......Tom