GOVERNORSGeneral & Speed LimitsSection 5GOVERNORSTHE PURPOSE OF THE GOVERNOR IS TO MAINTAINWITHIN CERTAIN LIMITS, A DESIRED ENGINESPEED, EVEN THOUGH THE LOAD MAY VARY.AIR VANE GOVERNORThe governor spring tends to open the throttle. Airpressure against the air vane tends to close the throttle.The engine speed at which these two forces balance iscalled the governed speed. The governed speed can bevaried by changing governor spring tension, Fig. 1, orchanging governor spring, Fig. 2.CheckingWorn linkage or damaged governor springs should bereplaced to insure proper governor operation. If springor linkage is changed, check and adjust TOP NO LOADR.P.M., Fig. 1, or check TOP NO LOAD R.P.M., Fig. 2,with engine assembled.Fig. 1. Air Vane Governor (Typical)Fig. 2. Air Vane Governor (Typical)MECHANICAL GOVERNORThe governor spring tends to pull the throttle open. Theforce of the counterweights, which are operated bycentrifugal force, tends to close the throttle. The enginespeed at which these two forces balance is called thegoverned speed. The governed speed can be varied bychanging governor spring tension or governor spring.See Fig. 3.Fig. 3. Mechanical GovernorGOVERNED SPEED LIMITSTo comply with specified top governed speed limits,Briggs & Stratton supplies manufacturers with enginesusing either calibrated governor springs or an adjustabletop speed limit. Calibrated springs or an adjustable topspeed limit will allow no more than a desired topgoverned speed when the engine is operated on a rigidtest stand at our own Factory. However, the design ofthe cutter blade, deck, etc., can affect engine speeds.Therefore, the top governed speed should be checkedwith tachometer when the engine is operated on acompletely assembled machine. If on a lawn mower, itshould be operated on a hard surface to eliminate cuttingload on the blade.JUNE 19811
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