Yamaha F150B Service Manual page 201

c
d
Vacuum gauge c, d:
(commercially available)
TIP:
For best results, use a vacuum gauge (com-
mercially available), like c or d that has four
adapters.
2. Start the engine and warm it up for 5 min-
utes.
3. Check the vacuum pressure of all cylin-
ders.
4. Turn the synchronizing screw e so that
the each vacuum pressure of cylinder #3
or #4 is within 2.0 kPa (15.0 mmHg) of
the each vacuum pressure of cylinder #1
or #2.
a
a
b
e
TIP:
• To increase the vacuum pressure, turn the
synchronizing screw e in direction a.
• To decrease the vacuum pressure, turn the
synchronizing screw e in direction b.
Example:
Check results:
Cylinder #1
kPa 49.0 48.0
(mmHg) (370.0) (360.0)
Adjust the difference of the vacuum pressure
between cylinders #1 and #4 to within 2.0
kPa (15.0 mmHg).
Check results:
Cylinder #1
kPa 49.0 48.0
(mmHg) (370.0) (360.0)
Adjust the difference of the vacuum pressure
between cylinders #2 and #4 to within 2.0
kPa (15.0 mmHg).
5. Attach the special service tool f to
spark plug wire #1 g, and then check the
engine idle speed.
g
f
Digital tachometer f: 90890-06760
Engine idle speed: 650–750 r/min
Throttle body
#2 #3 #4
47.0 46.0
(350.0) (340.0)
#2 #3 #4
50.0 51.0
(370.0) (380.0)
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A