Checking The Valve Springs; Checking The Valve Lifters; Installing The Valves - Yamaha YZ250F(D) Owner's Service Manual

Yz series
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h. Press the valve through the valve
guide and onto the valve seat to
make a clear pattern.
i.
Measure the valve seat width
again. If the valve seat width is out
of specification, reface and relap
the valve seat.

CHECKING THE VALVE SPRINGS

1. Measure:
• Valve spring free length "a"
Out of specification → Replace.
Free length (valve
spring):
Intake:
39.76 mm (1.57 in)
<Limit>: 38.76 mm
(1.53 in)
Exhaust:
37.78 mm (1.49 in)
<Limit>: 36.78 mm
(1.45 in)
2. Measure:
• Compressed spring force "a"
Out of specification → Replace.
Compressed spring
force:
Intake:
99–114 N at 28.98 mm
(9.9–11.4 kg at 28.98
mm, 22.27–25.57 lb at
1.14 in)
Exhaust:
126–145 N at 28.30
mm (12.6–14.5 kg at
28.30 mm, 28.44–
31.97 lb at 1.11 in)
b.
Installed length
3. Measure:
• Spring tilt "a"
Out of specification → Replace.
Spring tilt limit:
Intake:
2.5°/1.7 mm (0.067 in)
Exhaust:
2.5°/1.6 mm (0.063 in)
VALVES AND VALVE SPRINGS

CHECKING THE VALVE LIFTERS

1. Inspect:
• Valve lifter
Scratches/damage → Replace
both lifters and cylinder head.

INSTALLING THE VALVES

1. Apply:
• Molybdenum disulfide oil
Onto the valve stem and valve
stem seal.
2. Install:
• Valve "1"
• Valve spring seat "2"
• Valve stem seal "3"
• Valve spring "4"
• Valve spring retainer "5"
To cylinder head.
• Make sure that each valve is in-
stalled in its original place, also re-
ferring to the painted color as
follows.
Intake (middle) "a": Sky blue
Intake (right/left) "b": not paint
Exhaust "c": Purple
• Install the valve springs with the
larger pitch "d" facing upward.
e. Smaller pitch
3. Install:
• Valve cotter
4-26
Install the valve cotters by compress-
ing the valve spring with the valve
spring compressor "1" and the valve
spring compressor attachment "2".
Valve spring compres-
sor:
YM-04019/90890-04019
Valve spring compressor
adapter 19.5 mm:
YM-04114
Valve spring compressor
attachment:
900890-04114
4. To secure the valve cotters onto
the valve stem, lightly tap the
valve tip with a piece of wood.
Hitting the valve tip with excessive
force could damage the valve.
5. Install:
• Adjusting pad "1"
• Valve lifter "2"
• Apply the molybdenum disulfide oil
on the valve stem end.
• Apply the engine oil on the valve lift-
ers.
• Valve lifter must turn smoothly
when rotated with a finger.
• Be careful to reinstall valve lifters
and pads in their original place.

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This manual is also suitable for:

Yz250f b 2012Yz250f 20122013 yz250f2013 yz250fd

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