Mount the crankshaft in the lathe centers or with the outer journals on prisms. Using an indicator installed near the central journal, measure the runout. If the runout is greater than 0.06, the shaft should be replaced.
Measure the diameters of the main and connecting rod journals with a micrometer (in two mutually perpendicular directions). Enter the measurement results into the table. Determine which group the neck sizes belong to (nominal, 1, 2, 3 repair).
Determine the calculated clearance value, assuming that the diameter measured by the liners is equal to the diameter of the corresponding repair group - see the Table of dimensional and installation data (Table 3). If the calculated clearance is less than 0.8 mm for main bearings and 0.07 for connecting rod bearings, do not re-grind the journals, but simply replace the bearings with new ones of the same group (although you don't have to change them). If the clearance is greater than 0.17 mm on the main journals and 0.1 mm on the connecting rod journals, then the corresponding journals (either all main or all connecting rod) should be reground to the closest repair diameter and used with new liners of the same group. Determine their ovality and taper. The maximum deviations should be considered to be 0.03 mm for ovality and 0.0 15 mm for taper. If the measurement results exceed those specified above, the journals should be reground, even if their diameter has not yet reached the maximum permissible value.
After regrinding the shaft and purchasing new liners, you should measure the true value of the clearances in the main and connecting rod bearings for verification. To do this, clean the liners, insert them into the sockets in the cylinder block, place the crankshaft on all the main journals and put pieces of plastic wire (figure 84). Install the main caps with the inserted liners and tighten the bolts to a torque of 65 Nm, after which the shaft can no longer be rotated.
To measure the clearance in the connecting rod bearings, the connecting rod should be brought to the journal of the shaft and pieces of plastic wire should be placed under the connecting rod cap, equipped with a liner. Tighten the connecting rod cap fastening nuts with a torque of 30 Nm, but in this case they should not be tightened by another 900. Since the shaft cannot be rotated, the clearance can only be measured on two connecting rod journals occupying the BDC position.
Remove the main bearing caps and both connecting rod bearing caps.
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Measure the width of the removed pieces of calibrated wire on the scale (see figure 84). The width value is numerically equal to the bearing clearance. If this clearance is greater than 0.03-0.08 mm for main bearings and 0.02-0.07 mm for connecting rod bearings, then the corresponding bearings must be replaced.
Then turn the crankshaft and measure the remaining connecting rod journals. The measurements should be taken in a similar manner. If the clearance exceeds the permissible value, replace the corresponding set of liners, and then measure the clearances again; they should fall within the permissible value range.
For reground journals and new liners, the clearance should be within 0.03-0.08 mm for main bearings and 0.02-0.07 for connecting rod bearings. If the values of these clearances are greater than these specified, but less than 0.17 and 0.1 mm, respectively, the engine can be operated, but this indicates that the diameters of the shaft journals were reduced more than the norm during grinding. If the clearance is greater than these values, the journals should be reground again.
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