Yamaha YZ125(W)/W1 Owner's Service Manual page 256

CYLINDER HEAD, CYLINDER AND PISTON
2. Inspect:
9 Cylinder inner surface
Score marks ¡ Repair or replace.
Use #400~600 grit wet sandpaper.
cC
Do not rebore the cylinder.
3. Measure:
9 Cylinder bore "C"
Use cylinder gauge 1.
Out of limit ¡ Replace.
NOTE:
Measure the cylinder bore "C" in parallel (A, B,
C) to and at right angles to the crankshaft (a, b).
Then, find the average of the measurements.
Cylinder 54.000~54.014mm
bore "C" (2.1260~2.1265 in)
Taper "T"
C=Maximum Aa~Cb
T=(Maximum Aa, or Ab) —
(Maximum Ba, or Bb)
EC474302
Piston
1. Eliminate:
9 Carbon deposits
From the piston crown
b.
2. Inspect:
9 Piston wall
Score marks ¡ Repair or replace.
3. Measure:
9 Piston skirt diameter
Use micrometer 1.
Measure the specific distance a from the
bottom edge.
Out of specification ¡ Replace.
Distance
17.5 mm
(0.69 in)
4-21
ENG
Standard Wear limit
54.1 mm
(2.130 in)
0.05 mm
—
(0.0020 in)
a and ring groove
a a
Piston dia.
53.957~53.972 mm
(2.1243~2.1249 in)