Carburetor Adjustment; Idle Speed Adjustment - Yamaha YXR660FAS Owner's Manual

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Carburetor adjustment

The carburetor is a vital part of the engine and
requires very sophisticated adjustment. Most
adjusting should be left to a Yamaha dealer
who has the professional knowledge and ex-
perience to do so. However, the idling speed
may be performed by the owner as a part of
the usual maintenance routine.
CAUTION:
_
The carburetor was set at the Yamaha fac-
tory after many tests. If the settings are
disturbed by someone without sufficient
technical knowledge, poor engine perfor-
mance and damage may result.
_
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Idle speed adjustment

NOTE:
_
A diagnostic tachometer must be used for this
procedure.
_
1. Start the engine and warm it up for a few
minutes at approximately 1,000 to
2,000 r/min. Occasionally rev the engine
to 4,000 to 5,000 r/min. The engine is
warm when it quickly responds to the
throttle.
2. Remove the seats. (See page 4-16 for
seat removal and installation procedures.)
3. Remove the console. (See page 8-8 for
console removal and installation proce-
dures.)
4. Connect the tachometer to the spark plug
lead, and then set the idle to the specified
idling speed by adjusting the throttle stop
screw. Turn the screw in direction a to
increase the engine speed, and in direc-
tion b to decrease the engine speed.
Specified idle speed:
1,450–1,550 r/min
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