Yamaha F150B, Service Manual

Page: 201 / 458

6-24
Throttle body
0
1
2
3
4
5
6
7
8
9
10
A
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.
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:
Adjust the difference of the vacuum pressure
between cylinders #1 and #4 to within 2.0
kPa (15.0 mmHg).
Check results:
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.
Vacuum gauge
c
,
d
:
(commercially available)
a
c
d
a
b
e
Cylinder #1 #2 #3 #4
kPa
(mmHg)
49.0
(370.0)
48.0
(360.0)
47.0
(350.0)
46.0
(340.0)
Cylinder #1 #2 #3 #4
kPa
(mmHg)
49.0
(370.0)
48.0
(360.0)
50.0
(370.0)
51.0
(380.0)
Digital tachometer
f
: 90890-06760
Engine idle speed: 650–750 r/min
g
f