Yamaha 2004 YP400 Service Manual page 245

CYLINDER AND PISTON
2. Measure:
• piston-to-cylinder clearance
M MMM M MMM M
a. Measure 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 mea-
surements.
Cylinder bore "C"
Taper limit "T"
"C" = maximum of D
"T" = maximum of D
D
5
b. If out of specification, rebore or replace the
cylinder, and replace the piston and piston
rings as a set.
c. Measure piston skirt diameter "P" with the
micrometer.
a 5 mm (0.20 in) from the bottom edge of the pis-
ton
Standard
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
f. If out of specification, rebore or replace the
cylinder, and replace the piston and piston
rings as a set.
L LLL L LLL L
5 - 32
ENG
M MMM M M MMM M M MMM M
83.000 ~ 83.010 mm
(3.2677 ~ 3.2681 in)
0.05 mm (0.002 in)
~ D
1 2
or D – maximum of
1 2
or D
6
Piston size "P"
82.930 ~ 82.945 mm
(3.2650 ~ 3.2656 in)
0.060 ~ 0.075 mm
(0.0024 ~ 0.0030 in)
<Limit>: 0.15 mm (0.0059 in)
L LLL L L LLL L L LLL L
M MMM M MMM
L LLL L LLL