Yamaha YZ250(P)/LC, Owner'S Service Manual

Page: 256 / 584

4-22
ENG
CYLINDER HEAD, CYLINDER AND PISTON
EC474200
Cylinder
1. Remove:
9
Carbon deposits
Use a rounded scraper
1
.
NOTE:
Do not use a sharp instrument. Avoid scratching
the aluminum.
2. Inspect:
9
Cylinder inner surface
Score marks
→
Repair or replace.
Use #400~600 grit wet sandpaper.
c C
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.
EC474320
Piston
1. Remove:
9
Carbon deposits
From the piston crown
a
and ring groove
b
.
2. Inspect:
9
Piston wall
Score marks
→
Repair or replace.
Standard Wear limit
Cylinder 66.400~66.414mm 66.5 mm
bore “C” (2.6142~2.6147 in) (2.618 in)
Taper
—
0.05 mm
“T” (0.0020 in)
C=Maximum Aa~Cb
T=(Maximum Aa, or Ab) —
(Maximum Ba, or Bb)
5NX-9-30-4A 6/5/01 4:13 PM Page 44