Fix the crankshaft in the centers or install the outer main journals on measuring prisms and use an indicator to check the runout of the main journals. The runout should not exceed 0.06 mm. If it exceeds this value, replace the crankshaft.
Measure the clearances in the main and connecting rod bearings:
- install the main bearing caps without liners into the cylinder block in accordance with the markings and tighten the nuts to a torque of 100 Nm.
- in accordance with Fig. 34, measure the diameter of the hole in directions A, B and C of each main bearing and record it. If the diameter or ovality of the hole increases within 0.02 mm, the defect can be eliminated by lapping on a marking plate using emery cloth.
- unscrew the covers, install the liners and tighten the nuts again.
- measure the diameters of the holes and write them down.
- subtract the diameter of the corresponding crankshaft journal from the bearing bore diameter. The clearance for main bearings should be within 0.035...0.075 mm, for connecting rod bearings 0.035...0.065 mm. The maximum clearance is 0.09 mm for main bearings and 0.08 mm for connecting rod bearings. If necessary, the clearance can be ensured by installing new liners.
Fig. 34. Measuring the diameter of the crankshaft main bearing.