GAS, OIL AND ALCOHOL ENGINES 429 



Some gum or scale under one side of the valve. If they 

 leak, it may be due to the fact that the valve seat has 

 become worn owing to excessive heat, in which case they 

 must be reground. If there are broken rings, they must 

 be replaced with new. If poorly seated, new rings must 

 be fitted to the cylinder. If they are gummed up so they 

 will not spring out against the cylinder walls, they may 

 be oiled and loosened with kerosene. 



573. Ignition. The majority of the gasoline engine 

 troubles may be laid to the ignitor. As stated before, it 

 is often very difficult to pick out the trouble with the 

 ignitor in the case of a battery which has been exhausted. 



If for any reason the operator thinks the spark fails 

 to pass on the inside of the cylinder, the wire on the in- 

 sulated terminal should be disconnected and snapped on 

 some bright part of the engine. If there is a spark, it 

 proves that as far as the battery is concerned everything 

 is satisfactory. If there is none, the wire should be thor- 

 oughly gone over, the trouble located, and a spark ob- 

 tained. Perhaps it will be found that a binding screw is 

 loose, or the circuit has been broken at some other point. 

 If the operator gets a spark in the above manner, and 

 then snaps the wire across the insulated binding post, 

 obtaining a spark, there is a connection between the 

 points within the engine, and the ignitor must be re- 

 moved and cleaned. If by making this test there is no 

 spark, it indicates that there is no circuit between the 

 ignitor points, and the operator should now hold the 

 points together within the engine, by means of the ignitor 

 dog, and snap the wire across the insulated terminal. 

 This time a spark should .be obtained, but if not, it indi- 

 cates that there is insulation between the points, which 

 must be cleaned after the ignitor is removed. Water and 

 carbon will make a circuit between the points, while oil 



