2.9.4. Check of technical condition

Clear the piston of a deposit and remove all deposits from lubricant channels of the piston and a rod.
Carefully examine details. Cracks of any character on the piston, piston rings, a finger, on a rod and its cover are not allowed. If on a working surface of inserts there are deep risks, then replace inserts new.

Fig. 2.39. Check of a gap between piston rings and flutes

Check a gap between piston rings and flutes a set of probes, as shown in fig. 2.39, inserting a ring into the corresponding flute. The nominal (settlement) gap for the top compression ring makes 0,04–0,075 mm, for lower – 0,03–0,065 mm and for oil scraper – 0,02–0,055 mm. Maximum permissible gaps at wear – 0,15 mm.

Fig. 2.40. Check of a gap in the lock of rings

Check a gap in the lock of piston rings a set of probes, inserting rings into caliber (fig. 2.40) having diameter of an opening equal to the nominal diameter of a ring with the admission of ±0,003 mm. It is possible to apply caliber to rings of the normal size with a diameter of 82 mm 67.8125.9502.
The gap has to be within 0,25–0,45 mm for all new rings. A maximum permissible gap at wear of 1 mm.