Crankshaft Main Bearing: Application and ID

MAIN BEARINGS

GENERAL INFORMATION
- Service main bearings are available in standard size and 0.25 mm (0.0098 inch) undersize, and standard size has 5 kinds of bearings differing in tolerance.
To distinguish undersize bearing, it is painted red at the position as indicated in figure. Undersize bearing thickness is 2.124 - 2.128 mm (0.0836 - 0.0337 inch) at the center of bearing.





- Upper half of bearing has oil groove as shown in figure. Install this half with oil groove to cylinder block.
- Lower half of bearing does not have oil groove.


SELECTION OF MAIN BEARINGS

STANDARD BEARING:
If bearing is in malcondition, or bearing clearance is out of specification, select a new standard bearing according to following procedure and install it.





1. First check journal diameter. As shown in figure, crank web No.2 has stamped numbers.





Three kinds of numbers ("1", "2" and "3") represent following journal diameters.
Stamped numbers on crank web No.2 represent journal diameters marked with an arrow in figure respectively.
For example, stamped number "1" indicates that corresponding journal diameter is 57.994 - 58.000 mm.
2. Next, check crankcase (bearing cap) bore diameter without bearing. On lower crankcase five alphabets are stamped as shown in figure.





Three kinds of alphabets ("A", "B" and "C") represent following cap bore diameters.
Stamped alphabets on lower crankcase represent crankcase bore diameter marked with an arrow in figure respectivery.
For example, stamped alphabet "A" indicates that corresponding bearing cap bore diameter is 62.000 - 62.006 mm.





3. There are five kinds of standard bearings differing in thickness. To distinguish them, they are painted in following colors at the position as indicated in figure.





Each color indicated following thickness at the center of bearing.
4. From number stamped on crank web No.2 and alphabets stamped on lower crankcase, determine new standard bearing to be installed to journal, by referring to table shown.





For example, if number stamped on crank web No.2 is "1 " and alphabet stamped on lower crankcase is "B", install a new standard bearing painted in "Black" to its journal.





5. Using gaging plastic, check bearing clearance with newly selected standard bearing.
If clearance still exceeds its limit, use next thicker bearing and recheck clearance.
If clearance can not be still brought to within its limit even by using a new standard size bearing, regrind the crank pin to under size and use 0.25 mm undersize bearing.

Crankshaft journal diameter (0.25 mm undersize): 57.698 - 57.744 mm (2.2716 - 2.2733 inch)

6. When replacing crankshaft or cylinder block and lower crank case due to any reason, select new standard bearings to be installed by referring to number stamped on new crankshaft or alphabets stamped on new lower crankcase.