Crankshaft Main Bearing: Service and Repair

CRANKSHAFT AND PISTON

CRANKSHAFT AND CRANKSHAFT BEARING
1) Clean the crankshaft completely and check for cracks by means of liquid penetrant tester etc., and replace if defective.





2) Measure the crankshaft bend, and correct or replace if it exceeds the limit.

NOTE: If a suitable V-block is not available, install the #1 and #5 crankshaft bearing on cylinder block, position the crankshaft on these bearings and measure the crankshaft bend using a dial gauge.

Crankshaft bend limit: 0.035 mm (0.0014 inch)








3) Inspect the crank journal and crank pin for wear. If they are not within the specifications, replace the bearing with a suitable (undersize) one, and then replace or recondition the crankshaft as necessary. When grinding the crank journal or crank pin, finish them to specified dimensions according to the undersize bearing to be used.
Crank pin and crank journal:
Out-of-roundness 0.005 mm (0.0002 inch) or less
Taper limit 0.006 mm (0.00024 inch)
Crank pin grinding limit (diameter) 51.750 mm (2.0374 inch) or less
Crank journal grinding limit (diameter) 59.750 mm (2.3524 inch) or less





4) Measure the thrust clearance of crankshaft at center bearing. If the clearance exceeds the limit, replace the bearing.
Crankshaft thrust clearance:
Standard 0.030 - 0.115 mm (0.0012 - 0.0045 inch)
Limit 0.25 mm (0.0098 inch)
5) Inspect individual crankshaft bearings for signs of flaking, seizure, melting, and wear.
6) Measure the oil clearance on each crankshaft bearing by means of plastigauge. If the measurement is not within the specification, replace the defective bearing with an undersize one, and replace or recondition the crankshaft as necessary.
Crankshaft oil clearance:
Standard 0.010 - 0.030 mm (0.0004 - 0.0012 inch)
Limit 0.040 mm (0.0016 inch)