Yamaha YZ250 2022, Owner'S Service Manual

Page: 170 / 274

CYLINDER HEAD, CYLINDER AND PISTON
5-8
e. If out of specification, replace the piston
and piston rings as a set.
f. Calculate the piston-to-cylinder clearance
with the following formula.
g. If out of specification, replace the cylinder,
and replace the piston and piston rings as
a set.
EAM30547
COMBINATION OF PISTON AND CYLINDER
1. Check:
•
Cylinder mark “a”
2. Check:
•
Piston mark “a”
3. Combination:
•
Combine the piston and cylinder by the fol-
lowing chart.
TIP
When you purchase a cylinder, you cannot des-
ignate its size. Choose the piston that matches
the above chart.
Diameter
66.352–66.367 mm (2.6123–
2.6129 in)
a. 17.5 mm (0.69 in) from the bottom edge of
the piston
Piston-to-cylinder clearance =
Cylinder bore - Piston skirt diameter
Piston-to-cylinder clearance
0.045–0.050 mm (0.0018–0.0020
in)
Cylinder mark “a” Cylinder size
A
66.400–66.402 mm
(2.61417–2.61425 in)
B
66.404–66.406 mm
(2.61433–2.61441 in)
C
66.408–66.410 mm
(2.61449–2.61457 in)
D
66.412–66.414 mm
(2.61465–2.61472 in)
a
b
Piston mark “a”
(color)
Piston size
A (red)
66.352–66.355 mm
(2.61228–2.61240 in)
B (orange)
66.356–66.359 mm
(2.61244–2.61256 in)
C (green)
66.360–66.363 mm
(2.61260–2.61272 in)
D (purple)
66.364–66.367 mm
(2.61276–2.61287 in)
Cylinder mark Piston mark (color)
A A (red)
B B (orange)
C C (green)
D D (purple)