Figure 3-4.–Liner before and after stoning.

Figure 3-4.–Liner before and after stoning. types of liner wear check are illustrated in figure 3-5. Excessive maximum diameter results from general wear equally around the cylinder. Out-of-roundness is produced by the piston thrusting against one or two sides of the cylinders. Clearance between a piston and a liner is generally checked by measuring both parts with a micrometer. On smaller engines, you can use a feeler gauge. Clearance in excess of that specified by the manufacturer is generally due to liner wear, which normally is greater than piston wear. To determine liner wear, take measurements at three levels in the liner. Take the first measurement slightly below the highest point to which the top ring travels; take the next measurement slightly above the lowest point of compression ring travel; and take the third measurement at a point about midway between the first two. (Record all readings, so that rapid wear of any particular cylinder liner will be evident.) If wear or out-of-roundness exists beyond specified limits, replace the liner. Figure 3-6 shows two examples of taking Figure 3-5.–Measurements for determining liner wear. Figure 3-6.–Measuring the inside of a cylinder liner. inside measurements. The liner shown in figure 3-6, view B, requires at least twice as many measurements as other types of liners because it is from an opposed piston. You will not get accurate measurements unless you position the caliper or gauge properly in the liner. Common errors in positioning are illustrated in views A and B of figure 3-7. Hold one end of the caliper firmly against the liner wall as shown in view A of figure 3-6. Then move the free end back and forth, and up and down, until you establish the true diameter of the liner. The moving end will trace a patch similar to that illustrated in figure 3-8. Considerable experience in using an inside micrometer or cylinder gauge is necessary to ensure accuracy. As a precaution against error, it is a good 3-5