Cylinder Measurement

Measuring Piston Diameter, Diesel Engine

A cylinder dial gauge is required to measure the cylinder bore at the middle and bottom of the cylinder. If a dial gauge is not available, the following work cannot be carried out. Measure the cylinders in both the longitudinal and transverse directions. Measurements must be taken 15 mm from the top edge, 15 mm from the bottom edge and at the middle. A total of 6 measurements are required. Record all measurement results and compare them with the values given in the Specifications table. Note that all cylinders must be bored, even if only one cylinder is outside the specified dimensions. A deviation of 0.20 mm from the specified value means the cylinder must be bored. Pistons are available in only one oversize.
The final cylinder size is determined by measuring the piston in accordance with Figure 11.1, i.e. 18.0 mm from the piston pin. Measurements are taken below the lowest piston ring groove. Add the piston clearance of 0.04–0.06 mm to the measured value. Also allow 0.02 mm for final honing if the cylinders must be bored. To check piston-to-cylinder clearance, measure the cylinder bore and piston diameter as described above and calculate the difference for each cylinder. If the result exceeds 0.20 mm, bore the cylinders to fit oversize pistons (only one size is available), since the clearance has reached the wear limit.