Removal; Inspection - Yamaha RS90GTZ Service Manual

CYLINDER HEAD

REMOVAL

1. Remove:
• Cylinder head bolts
TIP
• Loosen the bolts in the proper sequence as
shown.
• Loosen each bolt 1/2 of a turn at a time. After
all of the bolts are fully loosened, remove
them.

INSPECTION

1. Eliminate:
• Combustion chamber carbon deposits
(with a rounded scraper)
TIP
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.
Maximum cylinder head warpage:
0.10 mm (0.0039 in)
Measurement steps:
• Place a straightedge
gauge across the cylinder head.
• Measure the warpage.
• If the limit is exceeded, resurface the cylinder
head as follows.
• Place a 400 ~ 600 grit wet sandpaper on the
surface plate and resurface the cylinder head
using a figure-eight sanding pattern.
TIP
To ensure an even surface, rotate the cylinder
head several times.
5-29
ENG
and a thickness