1. Cylinder liners can be inspected for wear by either removing them from the cylinder block or leaving them in place (the cylinder head must of course be removed in both cases). If the liners are in the cylinder block, they should be fixed with special strips so as not to accidentally budge. However, if you disassembled the engine before removing the pistons, it is best to remove the liners to inspect them.
2. There is a 1-4 line mark on the top edge of each sleeve indicating the sleeve size class. The size class is defined as the average diameter of the liner, obtained by measuring at 6 different points, and is used to match the liner to the piston, which is also marked, but only with letters. The four piston size classes are designated by letters from "A" before "D", and the piston class "A" must be used with a sleeve marked with one line, class "IN"- with a sleeve marked with two lines, etc. Size classes of sleeves and pistons are specified in the Specifications.
3. Sleeves should be checked for ovality, taper, abrasion and scratches. Start by inspecting the tops of the shells. If they are worn, there will be a slight protrusion at the top of the piston stroke. The wear of liners and piston rings can be recognized even before the engine is dismantled by excessive oil consumption and a blue tint in the exhaust gas.
4. Using an internal micrometer, measure the diameter of the sleeves just below the lip and compare this with the diameter of the sleeves at the bottom of the sleeves, which is less subject to wear. Compare also the liner diameters in a direction parallel to the piston pin direction and at right angles to it to evaluate the liner ovality. The taper and ovality of the cases will decrease from their top down to their base.
5. In general, any difference between the values obtained, greater than 0.25 mm, indicates the need to replace the sleeves. If this difference does not exceed 0.25 mm, then it is possible that the excess clearance between the pistons and the walls of the liners can be reduced by installing new piston rings. If there is a protrusion on the top of the sleeves, the top ring on each piston must have a special notch. Otherwise, the protrusion must be removed with a whetstone. When replacing liners, the pistons and piston rings must also be replaced.