So, the engine speed is preset at the factory. the tube at the rear of the carby that connects to engine block is the governor.
When the fly wheel speeds up, it creates an increased vacuum in the cap above the carb so the diaphragm lifts and closes the poppet valve just enough to reduce the fuel air mix and the engine reducing it back to the preset throttle position. When a load is imposed on the engine it slows the fly wheel down reducing the vacuum in the carby cap above the diaphragm. The spring in the cap above the diaphragm forces the diaphragm down to open the valve and allow a greater amount of fuel/air mix in and so the cycle continues.
some people get touchy about calling it a "vacuum" and stress that it's actually "negative pressure", but the victa manual describes it as a vacuum so whatever. At any rate, it self regulates. That's my understanding anyway. Someone will probably correct me. You can adjust the idle speed I'm told with these carboy's, there is a thread on it on the web page here, I'll find it and post the link if you like. but from my understanding it only works on the full crank design, as that allows you to access the button and clip while the engine is running. The power torque the connection is down in a tight spot and not practical to access while the engine is running.
