Yamaha RS90RK, Service Manual

Page: 154 / 841

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INSP
ADJ
CARBURETOR TUNING
TUNING
CARBURETOR TUNING
The carburetors are set at the factory to run at tem-
peratures of 0 °C ~ –20 °C (32 °F ~ –4 °F) at sea
level. If the machine is to be operated under condi-
tions other than those specified above, the carbure-
tors must be properly adjusted. Special care should
be taken in carburetor setting so that the pistons
will not be damaged or will not seize.
CAUTION:
Before performing the carburetor tuning, make
sure that the following items are set to specifi-
cation.
• Engine idle speed
• Throttle cable free play
• Carburetor synchronization
Carburetor tuning data
1. Standard specifications
Type CVK40
Manufacturer KEIHIN
I.D. Mark 8ES1 00
Main jet (M.J.) #148
Pilot jet (P.J.) #45
Pilot screw (P.S.) 2 turns out
Float height 16 mm (0.63 in)
Idle speed 1,300 ~ 1,500 r/min
Mid-range and high speed tuning
Adjustments are normally not required, but may
sometimes be necessary, depending on tempera-
tures, altitude or both.
Mid-range speed and high speed tuning (from 1/4
to full-throttle) can be done by adjusting the main
jet.
CAUTION:
Never run the engine without the air filter case
installed. Severe engine damage may result.
1. Start the engine and operate the machine under
normal conditions to make sure that the engine
operates smoothly. Stop the engine.
2. Remove:
• Spark plugs