Yamaha TTR125LM, Owner'S Service Manual

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4 - 34
ENG
CYLINDER AND PISTON
2. Measure:
●
Piston-to-cylinder clearance
Piston-to-cylinder clearance measure-
ment steps:
1st step:
●
Measure the cylinder bore “C” with the cyl-
inder bore gauge.
Cylinder bore “C”
54.000 ~ 54.019 mm
(2.126 ~ 2.127 in)
Taper limit “T” 0.05 mm (0.002 in)
Out of round “R” 0.05 mm (0.002 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
●
If out of specification, replace the cylinder,
and replace the piston and piston rings as
set.
2nd step:
●
Measure the piston skirt diameter “P” with
a micrometer.
a
5 mm (0.20 in) from the piston bottom edge.
Piston size P
Standard
53.977 ~ 53.996 mm
(2.1251 ~ 2.1258 in)
●
If out of specification, replace the piston
and piston rings as a set.
3rd step:
●
Calculate the piston-to-cylinder clearance
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)
NOTE:
Measure the cylinder bore “C” in parallel to
and at right angles to the crankshaft. Then,
find the average of the measurements.