Yamaha yz250 2015, Руководство пользователя

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CYLINDER HEAD, CYLINDER AND PISTON
3. Measure:
• Cylinder bore "C"
Use cylinder gauge "1".
Out of specification
→
Replace.
Measure the cylinder bore "C" in par-
allel (A, B, C) to and at right angles to
the crankshaft (a, b). Then, find the
average of the measurements.
CHECKING THE PISTON
1. Eliminate:
• Carbon deposits
From the piston crown "a" and
ring groove "b".
2. Inspect:
• Piston wall
Score marks
→
Repair or replace.
3. Measure:
• Piston skirt diameter
Use micrometer "1".
Measure the specific distance "b"
from the stepped surface "a" on
inside of the piston.
Out of specification
→
Replace.
CHECKING THE PISTON PIN AND
SMALL END BEARING
1. Inspect:
• Piston pin
• Small end bearing
Signs of heat discoloration
→
Re-
place.
2. Measure:
• Piston pin outside diameter
Use micrometer "1".
Out of specification
→
Replace.
3. Check:
• Free play (when the piston pin "1"
is in place in the piston "2")
There should be no noticeable for
the play.
Free play exists
→
Replace piston
pin and/or piston.
4. Install:
• Small end bearing
• Piston pin
Into the small end of connecting
rod.
5. Check:
• Free play
There should be no noticeable
free play.
Free play exists
→
Inspect the
connecting rod for wear/Replace
the pin and/or connecting rod as
required.
CHECKING THE PISTON RING
1. Install:
• Piston ring
Into the cylinder.
Push the ring with the piston
crown.
2. Measure:
• End gap
Use a thickness gauge "1".
Out of specification
→
Replace.
Standard Wear limit
Cylinder
bore "C"
66.400–
66.414
mm
(2.6142–
2.6147 in)
66.500
mm
(2.6181 in)
Taper
"T"
—
0.050 mm
(0.0020 in)
"C" = Maximum Aa–Cb
"T" = (Maximum Aa, or Ab) - (Max-
imum Ba, or Bb)
Dis-
tance
"b"
Piston diameter
17.5
mm
(0.69 in)
66.352–66.367
mm (2.6123–
2.6129 in)
Piston pin outside diam-
eter:
Standard <Limit>
17.995–18.000
mm (0.7085–
0.7087 in)
17.975 mm
(0.7077 in)
Ring end gap (installed):
Standard <Limit>
0.40–0.55 mm
(0.0157–0.0217
in)
0.95 mm (0.0374
in)