Checking The Main Bearing - APRILIA M192M Workshop Manual

ENGINE
3.5.5.

CHECKING THE MAIN BEARING

•
Optimal lubrication pressure (4 bar) and good oil deliv-
ery are necessary to ensure good lubrication. Bearings
must be correctly positioned so to prevent choking of
oil delivery lines.
•
Main bearings are composed of two half-bearings; one
is solid, the other is provided with special slots for lu-
brication.
•
The solid half-bearing withstands the thrusts due to
combustion and is positioned opposite the cylinder.
• To prevent choking of the oil delivery lines, the mating
surface of the two half bearings must be at right angles
to the cylinder axis.
• The section of the ducts is influenced by the depth to
which the bearings are driven.
Standard driving depth: 1,35 ÷ 1,6
NOTE To keep bearings in their correct position on casing,
they are fine-fitted on steel rings when the casings are cast.
• Check bearings diameter in the three directions.
• Repeat readings on the other half bearing.
NOTE Do not take readings on the mating surface between
the two shells, as the outer edges are chamfered to allow
distortion during driving operations.
•
Standard bearing diameter after driving varies is de-
termined by the coupling class.
•
Bearing locations on casing are classified into 2 cate-
gories, like the crankshaft, namely Cat. 1 and Cat. 2.
•
Bearings are divided into three categories, based on
the thickness. See table below:
TYPE
A
B
C
3 - 76
Engines M192M / M191M / M245M / M234M / M282M / M281M
DESCRIPTION
Red
Blue
Yellow