Yamaha F100A Service Manual page 70

INSP
ADJ
5
#1
#2
4
#3
#4
CONTROL SYSTEM
1
2
3
1
a
b
4
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
Direction b
Engine idling speed:
900 ± 50 r/min
Measure the vacuum pressure of car-
buretor #4.
Turn the
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.
3-4
Engine idling speed
increases.
Engine idling speed
decreases.
throttle valve adjusting
E