Yamaha 2003 YFZ450S, Service Manual

Page: 163 / 375

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ENG
CYLINDER HEAD
REMOVING THE CYLINDER HEAD
1. Remove:
• cylinder head
NOTE:
• Loosen the bolts in the proper sequence.
• Follow the numerical order shown in the illus-
tration. Loosen each bolt 1/4 of a turn at a
time until all of the bolts are loose.
EBS00230
CHECKING THE CYLINDER HEAD
1. Eliminate:
• combustion chamber carbon deposits
(with a rounded scraper)
NOTE:
_
Do not use a sharp instrument to avoid damag-
ing or scratching:
• spark plug bore threads
• valve seats
2. Check:
• cylinder head
Damage/scratches
→
Replace.
• cylinder head water jacket
Mineral deposits/rust
→
Eliminate.
3. Measure:
• cylinder head warpage
Out of specification
→
Resurface the cylin-
der head.
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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 cylin-
der 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.
Maximum cylinder head warpage
0.05 mm (0.002 in)