It will be required to you: portable lamp, set of flat probes, ruler, caliper, nutromer, micrometer, shaber.

After dismantling carefully wash up details kerosene, blow and dry them compressed air (especially oil channels of details).

1. Examine the block, especially attentively support of a bent shaft. Cracks in any places of the block are not allowed.

Good advice If there is a suspicion on existence of cracks in the block (hit of cooling liquid in a case or oils in cooling liquid), check tightness of the block at the special stand. You carry out an inspection in the repair shops having the corresponding equipment.

2. Examine cylinders on both sides. Scratches, teases and cracks are not allowed.

Good advice At survey of cylinders we recommend to light mirrors of cylinders with a portable lamp — so defects are visible much better.

Fig. 5.8. Scheme of measurement of cylinders: And – a belt of the greatest wear; B – a measurement zone after boring and a honingovaniye; In – a belt of the smallest wear

3. Determine by a nutromer the actual diameters of cylinders. Measure diameter of the cylinder in three belts (fig. 5.8). In each belt diameter is measured in two mutually perpendicular directions (longitudinal and cross). In a zone over a belt A (at distance of 5 mm from the socket plane with a block head) cylinders practically do not wear out. On a difference of the sizes in this zone and in other belts it is possible to judge wear of cylinders. The nominal sizes of cylinders are specified in tab. 5.9. Ovality and conicity should not exceed 0,065 mm. If the maximum value of wear is more than 0,15 mm or ovality exceeds the specified value, chisel cylinders to the closest repair size of pistons, having left an allowance of 0,03 mm for diameter under a honingovaniye. Then an otkhoninguyta cylinders, maintaining such diameter that at installation of the chosen repair piston the settlement gap between it and the cylinder was 0,03 mm. You carry out troubleshooting, boring and a honingovaniye of the block in the workshops having the special equipment.

4. Check a deviation from planeness of a surface of the socket of the block with a head of the block of cylinders. Apply a caliper (or a ruler) to the plane:

– in the middle of the block;

– in the cross and longitudinal directions;

– on plane diagonals. In each situation determine by the flat probe a gap between a caliper and the plane. It will also be a deviation from planeness. If the deviation exceeds 0,1 mm, replace the block.

5. Clear of a deposit the piston bottom a shaber (it is possible to make of an old file).

6. Clear of a flute deposit under piston rings an old ring, having inserted it into a flute the outer side and rolling on a flute.

7. Examine pistons, rods, covers: on them there should not be cracks.	8. Examine inserts: if on a working surface you find risks, teases and peelings of an antifrictional layer, replace inserts new. All connecting rods are identical and interchangeable.

9. Measure diameter of pistons in the plane, a perpendicular axis of a piston finger, at distance of 19 mm from a skirt edge. Diameters of pistons of the nominal size are specified in tab. 5.10, diameters of repair pistons are increased by 0,29 and 0,50 mm. By results of measurements define a gap between the piston and the cylinder, if necessary pick up new pistons to cylinders. The settlement gap between the piston and the cylinder (for new details) makes 0,03 mm. It is determined by a measurement of cylinders and pistons and provided with installation of pistons nominal or the repair sizes. The most admissible gap (at wear of details) – 0,15 mm. If at the engine which was in operation, the gap exceeds 0,15 mm, it is necessary to pick up pistons of the nominal size to cylinders or to install pistons of the repair size with boring and a honingovaniye of cylinders: the gap has to be as close as possible to settlement.

10. Check the flat probe a gap on height between flutes in the piston and rings, inserting a ring into the corresponding flute. The nominal (settlement) gap for both compression rings makes 0,020 mm. If the ring is big on height and the gap is small, bring ring height to the necessary value, grinding it on the emery paper laid on a glass plate.	11. Check the flat probe a gap in the lock of rings, having installed a ring in the cylinder on depth about 50 mm.

Good advice To establish a ring without distortion, advance a ring deep into of the cylinder the piston. The gap has to make 0,30–0,50 mm for both compression rings and 0,40–1,40 mm for an oil scraper ring. If a gap insufficient, cut butt surfaces of a ring. If the gap exceeds admissible, replace a ring.

12. All pistons of the nominal and repair sizes are manufactured with a fine precision and do not demand preliminary sorting and selection for weight. If necessary it is possible to install the pistons which were in the use in separate cylinders if they in good shape. Balancing of the engine in this case will not be broken.

13. Clear the surfaces of piston fingers of varnish deposits, previously having softened them in solvent. Examine fingers. If on them cracks, excessive wear in the place of contact with lugs of the piston and traces from a provorachivaniye in the top head of a rod are found, replace fingers. Check interface of a piston finger and the piston, implanting the finger which is previously oiled engine into a piston lug opening. At the ambient temperature of 20 °C the finger has to enter an opening when pressing a thumb of a hand and not drop out of a lug in vertical position of the piston with a piston finger. The finger which is dropping out of a lug should be replaced with another. If the finger drops out again, replace the piston with a finger (tab. 5.11).

14. Measure by a nutromer the internal diameter of Dv of a seat of a rod assembled with a cover.

Note Before measurement tighten conrod bolts the nominal moment.

15. Measure by a micrometer thickness of T of connecting rods.

Good advice In the absence of a special nozzle on a micrometer for measurement of a concave surface of an insert it is possible to use a small ball. After measurement of an insert it will be necessary to subtract diameter of a ball from the received size.

16. Measure by a micrometer diameter of Dn of conrod necks.

17. Calculate z gap between connecting rods and necks of a bent shaft on a formula z = Dv-2T-Dн. The nominal settlement gap makes 0,011–0,058 mm. If the actual settlement gap is less than limit, it is possible to use inserts which were established again. If the gap is more than limit, replace inserts on these necks new (nominal thickness).

If necks of a bent shaft are worn-out also pereshlifovana to the repair size reduced by 0,25 mm, replace inserts repair (the increased thickness).

Necks grind besides existence of the general wear if on them there are zaboina and risks or ovality makes more than 0,004 mm, and conicity — more than 0,005 mm.

18. Examine the top and lower inserts of radical bearings. Inserts of the central (third) radical bearing differ from the others in bigger width. Besides, at their side end faces the wide fillets playing a role of basic half rings of the persistent bearing of a bent shaft are executed. If on a working surface of inserts there were risks, teases, peelings of an antifrictional layer, replace inserts new.

Prevention It is forbidden to perform any subracing operations on inserts.

19. Examine a bent shaft. Cracks are not allowed. On the surfaces interfaced to working edges of epiploons there should not be scratches, забоин, рисок. At detection replace them a shaft.

20. Measure by a micrometer the outer diameter of Dn of radical necks. The actual gap between inserts of radical bearings and radical necks of a bent shaft is determined by the technique stated for connecting rods. The nominal settlement gap makes 0,005 mm. If the actual settlement gap is less than limit, it is possible to use inserts which were established again. If the gap is more than limit, replace on these necks inserts new (nominal thickness).

If necks of a bent shaft are worn-out also pereshlifovana to the repair size with reduction of diameter by 0,25 mm, replace inserts repair (the increased thickness).

Necks grind besides wear existence if on them there are zaboina and risks or ovality makes more than 0,004 mm, and conicity — more than 0,005 mm, reducing diameter by 0,25 mm (tab. 5.12).

21. Examine a bed of a bent shaft. Cracks, scratches, faces and risks are not allowed. Establish to the place of a cover of radical bearings and measure by a nutromer internal diameter (see tab. 5.12).

22. Check parallelism of persistent fillets of an average radical neck: if they are nonparallel, the bent shaft is bent and has to be replaced.