Yamaha F40BMHD, Service Manual

Page: 258 / 537

POWR
5-45
CRANKSHAFT AND PISTON
E
CHECKING THE MAIN-BEARING OIL
CLEARANCE
NOTE:
Make sure that the crankshaft is qualified
before initiating the following procedure.
1. Measure:
• Main-bearing oil clearance
Out of specification
→
Replace the
upper and lower bearings as a set.
NOTE:
Measure the main-bearing oil clearance at
room temperature (20 °C (68 °F)).
Measuring steps
CAUTION:
Install the bearings in their original posi-
tions. Incorrect oil clearance measure-
ments can lead to engine damage.
(1) Clean the bearings, main journals, and
bearing portions of the crankcase and
cylinder block.
(2) Place the cylinder block upside down
on a bench.
(3) Install half of the bearings and the
crankshaft into the cylinder block
.
NOTE:
Align the projection of the bearing with
the notch in the cylinder body.
(4) Put a piece of Plastigauge
®
on each
main journal in parallel to the crank-
shaft.
NOTE:
Do not put the Plastigauge
®
over the oil
hole in the main journal of the crankshaft.
Main-bearing oil clearance
0.012 - 0.044 mm
(0.0005 - 0.0017 in)
3
2
1
a
1
2
3
a