POWER ON THE FARM 399 



should be closely followed. If gummy oil or carbon collects 

 on the valves they should be cleaned to prevent leaks of gas. 



Engine Troubles. The chief engine troubles are associ- 

 ated with one or more of the four essentials which have just 

 been considered. The operator should learn to reason regard- 

 ing each of these and determine the probable cause of any 

 trouble. Get United States Farmers' Bulletin 1013 and 

 check over the trouble chart for gas engines. 



A common trouble comes from the use of too little oil in 

 lubricating the engine. The rings of the piston are apt to 



FIG. 252. Threshing wheat with the power of a tractor. (Cleveland Tractor Co.) 



get dry and stick; this causes trouble with the compression. 

 Too much oil in the cylinder will cause carbon deposit, as 

 shown by blue smoke from the exhaust pipe. This causes 

 over-heating and loss of power. Oil of proper quality should 

 be used. If the machine is one which supplies oil from the 

 crank case this should be cleaned out occasionally. 



Starting Troubles. It is more common to find troubles 

 in starting an engine than at any other time. When it is 

 impossible to get a single explosion, trouble is likely to be in 

 the mixture. The fuel may be flooded into the cylinder, 

 in which case the supply should be cut off and the cylinder 

 emptied by a few revolutions of the crank. The supply of 

 gas may be too low or too cold. Usually the mixture will 



