A cylinder dial indicator is required to measure cylinders (pic. 89), with which you can measure in the middle and at the bottom of the cylinder. If the dial indicator is missing, the following work cannot be carried out. Measure the cylinders in the longitudinal and transverse directions. In addition, measurements should be taken 15mm from the top edge, 15mm from the bottom edge and in the middle. A total of 6 measurements are required. Record all measurement results and compare with the data given in the size and adjustment tables. Please note that all cylinders must be bored, even if the dimensions of only one cylinder differ from the required dimensions. A deviation of 0.20 mm from the required value means that the cylinder must be bored. Pistons have only one repair size. The final size of the cylinder is determined by measuring the piston according to the data in Figure 314, that is, 18.0 mm from the piston pin. Measurements are taken under the lowest groove of the piston. The piston clearance of 0.04-0.06 mm should be added to the measured value. In addition, an allowance of 0.02 mm should be taken into account for final honing in case the cylinders are to be bored. To check piston play, measure the cylinder diameters and piston diameters as described above and calculate the difference for each cylinder. If the result exceeds 0.20 mm, the cylinders should be bored to install oversized pistons (only one size available), since the backlash has reached the wear limit.
Pic. 314. Measuring piston diameter on a diesel engine.