7-4
Chapter 7 ASSEMBLY OF BASIC ENGINE
1.3 Upper Main Bearing - Install
(1) Clean the main bearing fitting bore and main bearing
cap mating surfaces using cleaning solvent, and make
sure that these surfaces are free from any foreign mate-
rial.
(2) Make sure that the main bearing is free from damage
and contamination.
(3) Fit the upper main bearing shell in the crankcase bore
aligning the lug on the shell with the lug slot in the
crankcase.
Note:(a) Make the main bearing crush heights even at both
ends.
(b) The oil hole in the upper main bearing shell is
aligned with the oil hole in the crankcase by align-
ing the lug on upper shell with the lug slot in the
crankcase.
(4) Apply an even coat of clean engine oil to the sliding
surface of upper main bearing shell.
Upper Main Bearing - Install
(a) Do not apply engine oil to the back face of the main bearing shell and main bearing fitting bore in the crank-
case when installing the main bearing.Install the main bearing only after cleaning off foreign material, oil and
grease from these surface using cleaning solvent.
(b) When installing main bearings, be careful not to confuse the upper shell with lower shell.
The upper main bearing shell is identified by machined oil hole. The lower main bearing shell has no oil hole
nor groove.Be careful not to install the main bearing upside down.
(c) Be careful not to damage the bearing when installing.
Oil hole
Main bearing upper
Lug slot
Oil hole
Lug slot
Main bearing upper
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