Removing The Cylinder Head; Checking The Timing Chain Guide (Exhaust Side); Checking The Cylinder Head - Yamaha MTN850-A 2017 Service Manual

EAS30276

REMOVING THE CYLINDER HEAD

1. Remove:
• Intake camshaft
• Exhaust camshaft
Refer to "REMOVING THE CAMSHAFTS"
on page 5-11.
2. Remove:
• Cylinder head bolt (M6) (4)
• Cylinder head bolt (M9) (8)
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.
11
5
1
3
8
10
EAS30278
CHECKING THE TIMING CHAIN GUIDE
(EXHAUST SIDE)
1. Check:
• Timing chain guide (exhaust side)
Damage/wear  Replace.
EAS30277

CHECKING THE CYLINDER HEAD

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
9
7
4
2
6
12
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 cylinder
head.
Warpage limit
4
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a. Place a straightedge "1" and a thickness
8
gauge "2" across the cylinder head.
Thickness gauge
Feeler gauge set
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.
TIP
To ensure an even surface, rotate the cylinder
head several times.
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5-20
CYLINDER HEAD
0.10 mm (0.0039 in)
90890-03180
YU-26900-9