Popular Science Monthly 



not always necessary to use guiding 

 strips of metal when replacing rings as 

 it is often possible, by putting the rings 

 on the piston a little askew and man- 

 ceuvering them to pass the grooves with- 

 out springing the ring into them. The 

 top ring should be the last one placed in 

 position. 



Before replacing pistons in the cylin- 

 der one should make sure that the slots 

 in the piston rings are spaced equidistant 

 on the piston and if pins are used to keep 

 the ring from turning one should be care- 

 ful to make sure that these pins fit into 

 their holes in the ring and that they are 



Fig. 14. Showing method of sup- 

 porting crankcase to provide ready 

 access to connecting rod and 

 crankshaft bearings 



not under the ring at any point. The 

 cylinder should be well oiled before at- 

 tempt is made to install the pistons. The 

 engine should be run with more than the 

 ordinary amount of lubricant for several 

 days after new piston rings have been 

 inserted. 



Inspection and Refitting of Enc/ine 

 Bearings 



While the engine is dismantled one 

 has an excellent ojiportunity to examine 

 the various bearing points in the engine 

 crankcase to ascertain if any looseness 

 exists due to depreciation of the bearing 



135 



surfaces. As will be evident from the 

 views at Figs. 14 and 15, both main 

 crankshaft bearings and the lower end of 

 the connecting rods may be easily exam- 

 ined for deterioration. With the rods in 

 place as shown at Fig. 14, A, it is not 

 difficult to feel the amount of lost mo- 

 tion by grasping the connecting rod firm- 

 ly with the hand and moving it up and 

 down. 



The appearance of the engine base af- 

 ter the connecting rods and flywheel 

 have been removed from the crankshaft 

 is shown at Fig. 15, while the appear- 

 ance of the upper portion of the crank- 

 case, after the crankshaft is removed is 

 clearly shown at Fig. 14, C. 



After the connecting rods have been 

 removed and the flywheel taken ofif the 

 crankshaft to permit of ready handling 

 any looseness in the main bearing may be 

 detected by lifting upon either the front 

 or rear end of the crankshaft and ob- 

 serving if there is any lost motion be- 

 tween the shaft journal and the main 

 bearing caps. It is not necessary to take 

 an engine entirely apart to examine the 

 main bearings as in some forms these 

 mav be readily reached by removing a 

 large inspection plate either from the 

 bottom or side of the engine crankcase. 

 The symptoms of worn main bearings 

 are not hard to identify. If an engine 

 knocks when a vehicle is traveling over 

 level roads regardless of speed or spark 

 lever position and the trouble is not due 

 to carbon deposits in the combustion 

 chamber one may reasonably surmise 

 that the main bearings have become loose 

 or that lost motion may exist at the con- 

 necting rod big ends, and possibly at the 

 wrist pins. 



Adjusting Main Bearings 



When the bearings are not worn 

 enough to require refitting the lost mo- 

 tion can often be eliminated by remov- 

 ing one or more of the thin shims or 

 liners ordinarily used to separate the 

 bearing caps from the seat. Care must 

 be taken that an even number of shims 

 of the same thickness are removed from 

 each side of the journal. If there is con- 

 siderable lost motion after one or two 

 shims have been removed, it will be ad- 

 visable to take out more shims and to 



