Every time you remove a piston assembly from an engine, inspect it for wear. Measure the piston pins and sleeve bearings or bushings with a micrometer, as shown in figure 3-25, to determine whether wear is excessive. Do NOT measure areas that do not make contact. Such areas include those between the connecting rod and piston bosses and areas under the oil holes and grooves. You can press bushings out of the rod with a mandrel and an arbor press or with special tools, as shown in figure 3-26. You can also remove bushings by firt shrinking them with dry ice. Dry ice will also make it easier to insert the new bushing.

Figure 3-25.Measuring a piston pin and piston bushing for wear.

Figure 3-26.Removing or installing a piston pin bushing.

When you insert new bushings, be sure that the bore into which they are pressed is clean and that the oil holes in the bushing and the oil passages in the rod are aligned. To obtain proper clearance, sometimes you will need to ream a piston pin bushing after it has been installed. Figure 3-27 shows equipment used to ream a bushing. After installing a new bushing, check the alignment of the rod with equipment such as illustrated in figure 3-28. Be sure to check the manufacturers technical manual for details concerning clearances and alignment procedures.