Removing The Cylinder Head; Checking The Cylinder Head; Installing The Cylinder Head - Yamaha WR250R Service Manual

EAS24130

REMOVING THE CYLINDER HEAD

1. Remove:
Cylinder head bolts "1" (M6×60)
G
Cylinder head bolts "2" (M10×154)
G
Cylinder head bolts "3" (M10×140)
G
NOTE:
Gradually loosen bolts "a" to "f" in this sequence
in several times.
3
e
2
c
b
EAS24160

CHECKING THE CYLINDER HEAD

1. Eliminate:
Combustion chamber carbon deposits
G
(with a rounded scraper)
NOTE:
Do not use a sharp instrument to avoid damag-
ing or scratching:
Spark plug bore threads
G
Valve seats
G
2. Check:
Cylinder head
G
Damage/scratches → Replace.
Cylinder head water jacket
G
Mineral deposits/rust → Eliminate.
3. Measure:
Cylinder head warpage
G
Out of specification → Resurface the cylinder
head.
Cylinder head warpage
0.05 mm (0.002 in)
d
3
1
f
a
5-15
CYLINDER HEAD
MMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMM
a. Place a straightedge "1" and a thickness
gauge "2" across the cylinder head.
b. Measure the warpage.
c. If the limit is exceeded, resurface the cylinder
head as follows.
d. Place a 400–600 grit wet sandpaper on the
surface plate and resurface the cylinder head
using a figure-eight sanding pattern.
NOTE:
To ensure an even surface, turn the cylinder
head several times.
1
e. After resurfacing, out of specification → Re-
place the cylinder head.
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EAS24230

INSTALLING THE CYLINDER HEAD

1. Install:
Cylinder head gasket "1"
G
Dowel pins "2"
G
2
New