Yamaha YZ85W1 Service Manual page 165

CYLINDER HEAD, CYLINDER AND PISTON
2. Measure:
• piston-to-cylinder clearance
a. Measure cylinder bore "C" with the cylinder
bore gauge.
NOTE: NOTE:
Measure cylinder bore "C" by taking side-to-
side and front-to-back measurements of the
cylinder. Then, find the average of the mea-
surements.
Standard
Wear limit
Taper limit "T"
Out of round "R"
"C" = maximum of D
maximum of D
"T" =
maxmum of D
maximum of D
"R" =
minimum of D
b. If out of specification, replace the cylinder,
and the piston and piston rings as a set.
c. Measure piston skirt diameter "P" with the
micrometer.
20.0 mm (0.79 in) from the bottom edge of the
piston
Piston size "P"
Standard
47.457 ~ 47.472 mm (1.8684 ~ 1.8690 in)
d. If out of specification, replace the piston
and piston rings as a set.
e. Calculate the piston-to-cylinder clearance
with the following formula.
Piston-to-cylinder clearance =
Cylinder bore "C" –
Piston skirt diameter "P"
Piston-to-cylinder clearance
0.040 ~ 0.045 mm
(0.0016 ~ 0.0018 in)
<Limit>: 0.10 mm (0.0039 in)
f. If out of specification, replace the cylinder,
and the piston and piston rings as a set.
5-12
ENG
47.500 ~ 47.514 mm
(1.8701 ~ 1.8706 in)
47.6 mm (1.8740 in)
0.05 mm (0.0020 in)
0.05 mm (0.0020 in)
~ D
1 6
or D –
1 2
or D
5 6
D or D –
1 3 5
D or D
2 4 6