2. The grooves for the upper rings will most likely be the most worn. Once the grooves are clean, install the top rings into their grooves and check the side clearances with feeler gauges.
3. Carefully inspect the pistons for wear and damage. Check for fine hairline cracks around the piston pin holes.
4. If any of the pistons are obviously worn, damaged or burnt, the pistons must be replaced. A badly worn top piston ring groove on an otherwise good piston may need to be reamed to accept a thicker ring. If necessary, this can be a ring with a ledge so as not to touch the protrusion at the top of the sleeve. New pistons must match the class of their liners (see previous section). Disconnecting the pistons and connecting rods must be performed by a specialist, since the piston pin has an interference fit in the upper head of the connecting rod.
5. If the engine has not seized or has no serious damage, the connecting rods do not require special attention. It is enough to clean them and inspect them for obvious defects. If there is damage or uneven wear on the pistons, liners or bearings, it is advisable to check the connecting rods for warpage. This work requires special tools and should be performed by a specialist.
6. Before installing new rings on the pistons, it is necessary to measure their clearance in the lock. In principle, the gap should be adjusted at the factory, but if in doubt, you can insert the ring into the sleeve approximately to the middle of its height, check that it is positioned correctly and measure the gap in the lock using feeler gauges. A gap in the range of 0.254-1.016 mm is considered acceptable.
7. When installing new pistons with new piston rings in new liners, the ring gaps can be measured at the top of the liners, since new liners have no taper.
8. Install the lower oil scraper ring on the piston first, and then the second compression ring. This ring has a special chamfer, so it is necessary to ensure that it is installed in the correct position. The mark on the top surface of the ring should point towards the bottom of the piston. The next ring (the top one) can be installed in any position. The rings are installed in the reverse order of their removal. Be very careful, as compression rings are fragile and break easily.
