FARM MOTORS 



345 



liquid fuel into a gas. Kerosene and fuel oils are more diffi- 

 cult to vaporize, or gasify, than gasoline, and for that reason 

 a special carburetor must be provided when they are used; 

 but in other respects the kerosene 

 or fuel oil engine does not differ es- 

 sentially from the gasoline engine. 

 For this reason it is entirely cor- 

 rect to speak of all internal-com- 

 bustion engines burning either gas 

 or liquid fuels after this manner as 

 gas engines. 



The gas engine is very simple, 

 more so, in fact, 

 than the steam 

 engine. The 

 accuracy with 

 which the va- 

 rious functions 

 must be perform- 

 ed is the only thing which prevents the 

 gas engine from being a simple affair to operate. 



Types. There are two general types of gas engines on the 

 market. These are known as the two-cycle and the four- 

 cycle engines. It is perhaps more proper to style these types 

 as the two-stroke cycle and the four-stroke cycle, inasmuch as 

 two and four strokes of the piston are required to complete 

 the cycle in each type, respectively. 



A cycle is a term used to designate a complete set of 

 operations which must take place in every engine to enable it 

 to do work. The application of work or the liberation of energy 

 in the gas engine is intermittent. This is true of all recipro- 

 cating motors, but more operations are required in the gaso- 

 line engine than in the steam engine. The four-stroke cycle 



Fij 



buretor. 



Fig. 220. A kero- 

 sene carburetor in sec- 

 tion. One of the noz- 

 zles is for water. 



219. A gasoline car- 

 The gasoline is 

 vaporized by the air as it is 

 drawn past the nozzle. 



