Well, I just looked on mine, I got all the electronics back on it. The little brass fitting on mine does that as well, but it doesn't look like it is going to fall off or anything. The bolt (in place of your screw) moves with it as well. If your carburetor is working properly, then I wouldn't worry about it. Not any until I see fuel leaking out of it anyways...

Here are some pictures of my freshly cleaned truck. This is how I like 'em. It isn't that clean because I didn't take everything off and completely wipe down the chassis; I didn't have time to do that this time. However, after it gets dirty again, I'll probably do that. Cleaning the fuel tank and surrounding areas is what really gets you... Haha!