Removing The Cylinder Head; Checking The Cylinder Head - Yamaha 2004 YP400 Service Manual

Yamaha yp400(s) scooter service manual
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1
1
CYLINDER HEAD
EAS00222

REMOVING THE CYLINDER HEAD

1. Remove:
2
• cylinder head nuts
NOTE:
_
• Loosen the cylinder head nuts in the proper
sequence as shown.
3
• Loosen each cylinder head nut 1/2 of a turn
at a time. After all of the cylinder head nuts
are fully loosened, remove them.
EAS00229

CHECKING THE CYLINDER HEAD

1. Eliminate:
• combustion chamber carbon deposits
NOTE:
_
Do not use a sharp instrument to avoid damag-
ing or scratching:
• spark plug bore threads
• valve seats
2. Check:
• cylinder head
• cylinder head water jacket
3. Measure:
• cylinder head warpage
2
M
MMM
a. Place a straightedge 1 and a thickness
b. Measure the warpage.
c. If the limit is exceeded, resurface the cylin-
d. Place a 400 ~ 600 grit wet sandpaper on
NOTE:
_
To ensure an even surface, rotate the cylinder
head several times.
L
LLL
5 - 19
(with a rounded scraper)
Damage/scratches → Replace.
Mineral deposits/rust → Eliminate.
Out of specification → Resurface the cylin-
der head.
Maximum cylinder head warpage
0.05 mm (0.002 in)
M MMM
M
M MMM
M
M MMM
M
gauge 2 across the cylinder head.
der head as follows.
the surface plate and resurface the cylinder
head using a figure-eight sanding pattern.
L LLL
L
L LLL
L
L LLL
L
ENG
M MMM
M
M MMM
M
MMM
L LLL
L
L LLL
L
LLL

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2004 yp400s

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