Poor idling can usually be traced to some particle of foreign matter getting into the carburetor idling jet. To correct this, remove the jet and blow it out with compressed air, then hold it up to the light to make certain that it is absolutely clear. Once in a while in the machining operations a little burr so small, that it can hardly be detected without the aid of a magnifying glass, is formed in the jet and affects the idling. Removal of the burr corrects the trouble.