Yamaha F100A, Service Manual

Page: 70 / 463

3-4
INSP
ADJ
E
CONTROL SYSTEM
4. Adjust:
●
Carburetor synchronization
Adjustment steps:
●
Remove all of the plugs 1 .
●
Install the adaptors 2 and vacuum
gauge 3 onto the carburetor assembly
as shown.
Vacuum gauge set:
YU-08030/90890-03159
●
Start the engine and allow it to warm
up for several minutes.
●
Install the tachometer onto the spark
plug lead of cylinder #1.
Tachometer:
YU-08036-A/90890-06760
●
Adjust the engine idling speed to spec-
ification by turning the throttle stop
screw on carburetor #4
4 in direction
a
or
b
.
Direction
a
Engine idling speed
increases.
Direction
b
Engine idling speed
decreases.
Engine idling speed:
900
±
50 r/min
●
Measure the vacuum pressure of car-
buretor #4.
●
Turn the throttle valve adjusting
screws
5 so the vacuum pressure of
carburetors #1, #2, and #3 are the
same as carburetor #4.
●
Rev the engine a few times and make
sure the vacuum pressures stay within
50 mm Hg (67 m bar, 1.97 in Hg) of
each other. Also, make sure the engine
idling speed is stable.
●
Turn off the engine.
●
Remove the vacuum gauge and adap-
tors, and reinstall the plugs.
a
4
b
1
2
3
1
4
5
#1
#2
#3
#4