Yamaha MBK X-MAX 300 2017, Service Manual

Page: 264 / 462

CRANKSHAFT
5-69
5. Measure:
• Crankshaft-journal-to-crankshaft-journal
bearing clearance.
Out of specification
→
Replace the crank-
shaft journal bearings.
TIP
On the journal, the larger value is used as a ba-
sis for calculation of the oil clearance, and on the
journal bearing, the smaller value is used.
The following procedure applies to all of the
crankshaft journal bearings.
NOTICE
ECA13920
Do not interchange the crankshaft journal
bearings. To obtain the correct crankshaft-
journal-to-crankshaft-journal-bearing clear-
ance and prevent engine damage, the crank-
shaft journal bearings must be installed in
their original positions.
a. Clean the crankshaft journal bearings,
crankshaft journals, and bearing portions
of the crankcase.
b. Check the bearing surface. If the bearing
surface is worn or scratched, both bear-
ings should be replaced.
TIP
If either of the right or left journal bearing is worn
or scratched, both bearings should be replaced
as a set.
c. Measure the crankshaft journal diameter
“a” of each crankshaft journal. If it is out of
specification, replace the crankshaft.
d. Measure the crankshaft journal bearing in-
side diameter “b” of each crankshaft jour-
nal bearing.
TIP
Measure the crankshaft journal bearing inside
diameter at the distance “a” shown in the illustra-
tion.
e. If crankshaft journal bearing inside diame-
ter is “40.03” and crankshaft journal diam-
eter is “39.98”, then the journal oil
clearance is:
If the oil clearance is out of specification,
select replacement bearings.
6. Select:
• Crankshaft journal bearings (J
1
–J
2
)
TIP
• The numbers “A” stamped into the crankshaft
web and the numbers “B” on the crankcase are
used to determine the replacement crankshaft
journal bearing size.
Bearing color code
Code 1
Blue
Code 2
Black
Code 3
Brown
Code 4
Green
Journal oil clearance
0.031–0.064 mm (0.0012–0.0025
in)
Crankshaft journal diameter
39.976–40.000 mm (1.5739–
1.5748 in)
Crankshaft journal bearing inside
diameter
40.015–40.056 mm (1.5754–
1.5770 in)
a. 5.8 mm (0.24 in)
Journal oil clearance:
Crankshaft journal bearing inside diameter -
Crankshaft journal diameter
= 40.03 - 39.98
= 0.05 mm
a
b
a
b
a