To complete the work you will need a bore gauge and a piston ring mandrel.
Disassembly
1. Remove the piston rings from the piston (see "Piston rings and connecting rod bearings - replacement").
2. Using an awl or a screwdriver with a thin blade, pry up and remove the piston pin retaining ring from the groove.
Recommendation. If the grooves of the retaining rings are dented, nicked, and the rings are not securely fixed in them, the piston should be replaced.
3. Using a soft metal rod with a diameter of 16-18 mm, push out the piston pin and remove the piston from the connecting rod.
Examination
In new engines, the clearance between the piston and the cylinder is 0.025-0.045 mm and is set by installing pistons of the same class as the cylinders. The piston and cylinder class are designated by Latin letters which are stamped on the lower mating surface of the cylinder block...
...and on the piston bottom. The arrow on the piston points towards the front end of the crankshaft.
Note: For information on how to use the bore gauge, see the enclosed instructions or special literature.
1. Using a bore gauge, check the wear of the cylinder walls.
We take measurements in four zones (3, 10, 60 and 112 mm from the top edge of the cylinder) in the longitudinal and transverse directions of the engine. The upper belt does not wear out the cylinder. Based on the difference in bore gauge readings in different zones, we determine the degree of wear of each cylinder.
2. Using a micrometer to measure the diameter of the piston skirt, we determine its wear.
If the maximum wear is 0.7-5 mm or more, it is necessary to bore the cylinders and install pistons of a repair size, or replace the cylinder block and install new pistons.
In new engines, the clearance between the piston and the cylinder is 0.025-0.045 mm and is set by installing pistons of the same class as the cylinder class.
Assembly
We assemble the piston with the connecting rod in the reverse order of disassembly. In this case, the arrow on the piston bottom and the marks on the connecting rod and its cover should face the same direction.
