Yamaha YZ85(S)/LC, Owner'S Service Manual

Page: 234 / 506

4 - 19
ENG
3. Measure:
●
Cylinder bore “C”
Use cylinder gauge
1
.
Out of limit
→
Replace.
NOTE:
Measure the cylinder bore “C” in parallel (A, B,
C) to and at right angles to the crankshaft (a, b).
Then, find the average of the measurements.
Standard Wear limit
Cylinder
bore “C”
47.500 ~ 47.514 mm
(1.8701 ~ 1.8706 in)
47.6 mm
(1.8740 in)
Taper “T”
–
0.05 mm
(0.0020 in)
C = Maximum Aa ~ Cb
T = (Maximum Aa, or Ab) –
(Maximum Ba, or Bb)
5PA40490
5PA40500
Piston
1. Eliminate:
●
Carbon deposits
From the piston crown
a
and ring groove
b
.
2. Inspect:
●
Piston wall
Score marks
→
Replace.
3. Measure:
●
Piston skirt diameter
Use micrometer
1
.
Measure the specific distance
a
from the
bottom edge.
Out of specification
→
Replace.
Piston dia.:
47.457 ~ 47.472 mm
(1.8684 ~ 1.8690 in)
Distance
a
:
20 mm (0.79 in)
5PA40510
5PA40520
Piston pin and small end bearing
1. Inspect:
●
Piston pin
●
Small end bearing
Signs of heat discoloration
→
Replace.
5PA40530
CYLINDER HEAD, CYLINDER AND PISTON