FARM MOTORS 



359 



comparatively short time until the magneto will be consid- 

 ered a necessary part of the equipment of the gas engine. 

 At the present time the magneto is regarded as almost a 

 necessity in the operation of the automobile engine. In 

 selecting a magneto or dynamo, care should be taken to see 

 that it is well adapted to the service required and that it is 

 properly installed. 



Valve Action. The last of the four essentials for the suc- 

 cessful operation of the gas engine is proper valve action, or 

 the correct timing of the valves. It is obvious, after what 

 has already been written 

 on this subject, that the 

 valves must open at the 

 proper time to let the 

 gases into the cylinder, 

 close at the proper time 

 to withhold them for the 

 power stroke, and open 

 again to let the burned 

 gases escape. The suc- 

 tion or inlet valve on 

 farm engines is usually 

 operated by the suction produced by the piston during the 

 suction stroke, and, outside of the adjustment of the light 

 spring which closes the valve, it is self-timing. The exhaust 

 valve should open before the end of the expansion stroke, 

 to allow the free escape of the burned gases, and must 

 close at about the end of the exhaust stroke. The exhaust 

 valve for an average-sized engine is made to open when 

 the crank is about 30° from dead center, but the time will 

 vary with the speed and size of the engine. Directions 

 should be found with each engine for the setting of the 

 valves. 



Fig. 232. 



A dynamo called the Auto- 

 ^parker. 



