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CARBURETOR TUNING
SDN2760
SDN2770
2-36
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 intake si-
lencer installed. Severe engine damage may re-
sult.
1. Start the engine and operate the machine
under normal conditions to make sure that
the engine operates smoothly. Stop the en-
gine.
2. Remove:
•
Spark plugs
3. Check:
•
Spark plug insulator 1 color
A medium to light tan color indicates nor-
mal conditions.
Distinctly different color → Replace the
main jet.
4. The main jet should be adjusted on the basis
of the "Main jet selection chart".
NOTE:
By checking the condition of the spark plugs, it is
easy to get some idea of the condition of the
engine. This may diagnose potential problems
before engine damage occurs.
High altitude tuning
Use the chart in CHAPTER 9 to select main jets
according to variations in elevation and tempera-
ture.
NOTE:
These jetting specifications are subject to change.
Consult the latest technical information from
Yamaha to be sure you have the most up-to-date
jetting specifications.
1
Clip
2
Jet needle
3
Pilot mixture screw
4
Main jet
INSP
ADJ
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