Do you mean the throttle shaft? If the carb has been rebuilt, and the float level etc. is correct, then usually the trouble with a worn throttle shaft, is an airleak. The body can be drilled, and a brass insert put in to tighten up the play. You might see some wetness around the shaft when you first start up.
But, you can usually find a better carb at a swapmeet, or through friends, or the classifieds here on the bolt. No carb is going to work well unless it's rebuilt. Around here, a decent carb seems to run from $40-$60 at the swapmeet, and then you go to FLAPS to get a rebuild kit.
