Yamaha F15B Service Manual page 174

TRBL
SHTG
Symptom: The engine idle speed does not remain steady.
Check the throttle cable and link
operation.
Are they operat-
ing correctly?
Yes
Check the operation of the
carburetor.
Is the
carburetor operat-
ing correctly?
No
Check the pilot screw.
Is the pilot screw
setting correct?
Yes
Disassemble the carburetor and
check the internal parts.
Are the fuel or
air passages
clogged?
No
Check the throttle valve for
smooth operation.
Does the throttle
valve stick?
No
Check the ignition system or
compression system. Replace
if foulty parts.
9-5
Troubleshooting
No
Adjust the throttle cable and
throttle link.
Yes
Check the ignition system chart.
No
Adjust the pilot screw according
to specifications.
Using compressed air, clean the
Yes
pilot screw, needle valve, main
and pilot jets, and main nozzle.
Replace any damaged parts.
Yes
Correct or replace the carburetor.
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