Crankshaft Main Bearing: Service and Repair

HOW TO SELECT PISTON AND BEARING

Main Bearing


WHEN NEW CYLINDER BLOCK AND CRANKSHAFT ARE USED






1."MAIN BEARING SELECTION TABLE" rows correspond to bearing housing grade on rear side of cylinder block.










2."MAIN BEARING SELECTION TABLE" columns correspond to journal diameter grade on front side of crankshaft.





3.Select main bearing grade at the point where selected row and column meet in "MAIN BEARING SELECTION TABLE".

CAUTION:
- Initial clearance for No. 1, 5 journal and No. 2, 3, 4 journal is different. Use two different selection table for each part.
- No. 1, 5 journal and No. 2, 3, 4 journal have the same signs but different measures. Never confuse.
4.Apply sign at crossing in above step 3 to "MAIN BEARING GRADE TABLE".
NOTE:
- "MAIN BEARING GRADE TABLE" applies to all journals.
- Service parts are available as a set of both upper and lower.

WHEN CYLINDER BLOCK AND CRANKSHAFT ARE REUSED

1.Measure cylinder block main bearing housing inner diameter and crankshaft main journal diameter. Refer to EM.
2.Correspond the measured dimension in "Cylinder block main bearing housing inner diameter" row of
"MAIN BEARING SELECTION TABLE".
3.Correspond the measured dimension in "Crankshaft main journal diameter" column of "MAIN BEARING
SELECTION TABLE".
4.Follow from step 3 in "When New Cylinder Block and Crankshaft are Used".

MAIN BEARING SELECTION TABLE (No. 1 and 5 Journal)







MAIN BEARING SELECTION TABLE (No. 2, 3 and 4 Journal)







MAIN BEARING GRADE TABLE (ALL JOURNALS)

Main bearing grade table (All journals): Specifications.

UNDERSIZE BEARING USAGE GUIDE

- When the specified main bearing oil clearance is not obtained with standard size main bearings, use underside (US) bearing.
- When using undersize (US) bearing, measure the main bearing inner diameter with bearing installed, and grind main journal so that the main bearing oil clearance satisfies the standard.

CAUTION:





In grinding crankshaft main journal to use undersize bearings, keep the fillet R (A) [1.5 - 1.7 mm (0.059 - 0.067 in)].
Bearing undersize table: Specifications.