Yamaha RS90K, Service Manual

Page: 70 / 841

2-14
INSP
ADJ
CARBURETOR SYNCHRONIZATION/
ENGINE IDLE SPEED ADJUSTMENT
Adjustment steps:
• Synchronize carburetor #3 to carburetor #2 by
turning the synchronizing screw 1 in either
direction until both gauges read the same.
NOTE:
After each step, rev the engine two or three times,
each time for less than a second, and check the
synchronization again.
• Synchronize carburetor #3 to carburetor #1 by
turning the synchronizing screw
2
in either
direction until both gauges read the same.
NOTE:
The difference in vacuum pressure between two car-
buretors should not exceed 1.33 kPa (0.01 kg/cm
2
,
0.19 psi).
7. Measure:
• Engine idle speed
Out of specification
→
Adjust.
Make sure that the vacuum pressure is within
specification.
8. Stop the engine and remove the measuring
equipment.
9. Adjust:
• Throttle cable free play
Refer to “THROTTLE CABLE FREE PLAY
ADJUSTMENT”.
Vacuum pressure at engine idling
speed:
24.0 kPa (0.24 kg/cm
2
, 3.41 psi)
2
1
ENGINE IDLE SPEED ADJUSTMENT
NOTE:
Prior to adjusting the engine idling speed, the car-
buretor synchronization should be adjusted prop-
erly, the air filter should be clean, and the engine
should have adequate compression.
1. Start the engine and let it warm up for several
minutes.
2. Install:
• Engine tachometer
(near the spark plug)
Engine tachometer:
90793-80009, YU-08036-C