Yamaha YFM4FAR, Service Manual

Page: 159 / 397

4 - 29
ENG
CYLINDER AND PISTON
2.Measure:
●
Piston-to-cylinder clearance
*****************************************************
Measurement steps:
1st step:
●
Measure the cylinder bore “C” with the
cylinder bore gauge.
NOTE:
Measure cylinder bore “C” by taking side-to-
side and front-to-back measurements of the
cylinder. Then, find the average of the
measurements.
●
If out of specification, replace the cylinder,
and the piston and piston rings as a set.
Cylinder bore “C”
84.500 ~ 84.510 mm
(3.3268 ~ 3.3272 in)
Max. taper “T”
0.05 mm
(0.0016 in)
Out of round “R”
0.01 mm
(0.0004 in)
“C”= maximum of D
1
~ D
6
“T”= maximum of D
1
, or D
2
–
maximum of D
5
or D
6
“R”= maximum of D
1
, D
3
or D
5
–
minimum of D
2
, D
4
or D
6
2nd step:
●
Measure piston skirt diameter “P” with a
micrometer.
a
5.0 mm (0.20 in) from the piston bottom edge
●
If out of specification, replace the piston and
piston rings as a set.
Piston skirt diameter “P”
Standard
84.445 ~ 84.460 mm
(3.3246 ~ 3.3252 in)