Cylinder Servicing

Figure 3-29.—Tighten bolts in proper sequence. from becoming warped by storing it on end in a safe area. CYLINDER SERVICING There are certain limits to which cylinders may become tapered or out of round before they require refinishing. If they have only a slight taper or are only slightly out of round (consult the manufacturer’s manual for the maximum allow- able taper or out of round), new standard rings can be installed. When cylinder wear goes beyond the point recommended in the engine manufacturer’s speci- fications, loss of compression, high oil consump- tion, poor performance, and heavy carbon accumulations in the cylinder will result. In such cases, the only way to put the engine back into good operating condition is to refinish the cylinders and fit new pistons (or oversized pistons) and rings. CYLINDER WALLS CHECK As a first step in checking cylinder walls, wipe them clean and examine them carefully for scored places and spotty wear (which shows up as dark, unpolished spots on the walls). Holding a light at the opposite end of the cylinder from the eye will help in the examination. If scores or spots are found, you should refinish the cylinder walls. Next, measure the cylinders for taper and oval wear. This can be done with an inside micrometer or by a special dial indicator, as shown in figure 3-30. As the dial indicator is moved up and down in the cylinder and turned from one position to another, any irregularities will cause the needle to move. This will indicate how many thousandths of an inch the cylinder is out of round or tapered. The permissible amount of taper or out of roundness in a cylinder varies somewhat with different engines. Engine manufacturers issue Figure 3-30.—Dial indicator for measuring cylinders. recommendations based on experience with their own engine. When the recommendations are exceeded, the cylinders have to be refinished. CYLINDER REFINISHING There are two methods of refinishing cylinders: honing and boring. Cylinders are refinished by honing when wear is not too great; otherwise, they are bored with a machine, and oversized pistons and rings are installed. This machine consists of a boring bar and cutting tool, and operating the boring machine will vary among different makes of equipment. Consult the manu- facturer’s operating manual for the procedures recommended. 3-25