Yamaha TT-R125(R) Owner's Service Manual page 276

CYLINDER AND PISTON
2. Measure:
Piston-to-cylinder clearance
G
Piston-to-cylinder clearance measure-
ment steps:
1st step:
Measure the cylinder bore "C" with the cyl-
G
inder bore gauge.
NOTE:
Measure the cylinder bore "C" in parallel to
and at right angles to the crankshaft. Then,
find the average of the measurements.
Cylinder bore "C"
Taper limit "T"
Out of round "R"
"C" = maximum of D
"T" = maximum of D
maximum of D
"R" = maximum of D
minimum of D
If out of specification, replace the cylinder,
G
and replace the piston and piston rings as
set.
2nd step:
Measure the piston skirt diameter "P" with
G
a micrometer.
a 5 mm (0.20 in) from the piston bottom edge.
Standard
If out of specification, replace the piston
G
and piston rings as a set.
3rd step:
Calculate the piston-to-cylinder clearance
G
with following formula.
Piston-to-cylinder clearance =
Cylinder bore "C" –
Piston skirt diameter "P"
Piston-to-cylinder clearance:
0.020 ~ 0.026 mm
(0.0008 ~ 0.0010 in)
<Limit>: 0.15 mm (0.006 in)
4 - 34
ENG
54.000 ~ 54.019 mm
(2.126 ~ 2.127 in)
0.05 mm (0.002 in)
0.05 mm (0.002 in)
~ D
1 6
, or D –
1 2
or D
5 6
, D or D –
1 3 5
, D or D
2 4 6
Piston size P
53.977 ~ 53.996 mm
(2.1251 ~ 2.1258 in)