I've bought two or three 30/31's new and all have been great carbs right out of the box with nothing more than bolting them on needed.
One word of warning . . . if it was made in Brazil, keep an eye on the 5 screws on the top, the 4 screws on the accelerator pump and also the idle cut off solenoid. They have a tendency to work loose after a couple of months. If they do, just tighten 'em back up and you'll be fine. If it ever backfires through the carb with the air cleaner on, it might blow out the plug just above the throttle plate. If that ever happens, stick the plug back in, peen the edges to lock it in and then cover it with a little epoxy. If you can't find the plug, epoxy a dime back over the hole. It'll be fine.
Again, they are GREAT carbs, but they are not always put together as tight as they should be.