TM 10-3930-653-14&P Fig. 4-126. Figs.    6-8    and    6-9    show    the    operation    of    the governor valve under various operating conditions of the engine.    In  these  figures,  the  force  to  open  the  valve exerted  by  the  cam  and  cam  spring  is  indicated  by  a dotted  arrow,  the  force  to  close  the  valve  produced  by the pressure difference between both sides  of  the  valve is   shown   by   a   white   arrow,   and   that   effected   by   the stabilizer  piston  is  expressed  by  a  black  arrow;  and  the size of these arrows indicates the strength of force under each condition. Fig. 4-127. Fig. 4-128.  Negative Pressure is Large a. When the engine is stalled. The force to close the governor valve is absent, so it is fully opened by the action of the cam spring. b. During idling. Owing    to    a    large    negative    pressure    below    the throttle  valve,  the  stabilizer  piston  tends  to  be  sucked out, causing the governor valve to be almost closed. c. When    the    carburetor    throttle    valve    is    partially opened. When   the   engine   is   rotating   at   low   speed,   the pressure  difference  between  both  sides  of  the  governor valve   is   small,   exertising   only   a   small   force   on   the stabilizer piston, so the governor valve is kept fairly open. With  the  increase  of  engine  speed,  the  pressure difference  between  both  sides  of  the  governor  valve  as well   as   the   force   on   the   stabilizer   piston   increases, causing the valve to close. Fig. 4-129. 4-75