It has a governor that sets the speed depending on power output , usually 700 rpm for the standard 1.5 HP version. 1 HP engines are 500 rpm, 2 HP at 1000 RPM. There were other speeds available for special order but these are standard. There is an adjustable spring on the carburettor linkage that can apply more tension if you wish to increase the idle, or run it at a higher speed continuously.