KTM 450 SX ATV Owner's Manual page 143

MAINTENANCE ON CHASSIS AND ENGINE
Guideline
Choke function deactivated – The choke lever is pushed in to the stop. (
Idle speed
Info
If the idle speed is set significantly higher, the engine does not start. When the
electric starter button is activated, the electric starter turns over the engine, but
the engine does not start because there is no ignition spark.
–
Turn the idle adjusting screw
–
Note the position and turn the idle adjusting screw slowly counterclockwise until the
idle speed falls.
–
Adjust to the point between these two positions with the highest idle speed.
Info
If there is a large increase in the engine speed, reduce the idle speed to a nor-
mal level and repeat the above steps.
The extremely sporty rider will set the mixture about 1/4 of a turn back from this
ideal value (leaner, clockwise) since the engine has a higher operating tempera-
ture in sporting use.
If the procedure described here does not lead to satisfactory results, the cause
may be a wrongly dimensioned idling jet.
If you can turn the idle adjusting screw to the end without any change of engine
speed, you have to fit a smaller idling jet.
The idle adjusting screw must not be opened more than two turns. If more than
two turns are necessary (rich mixture), use a larger idling jet.
After changing the idling jet, start from the beginning with the adjusting steps.
–
Adjust the idle speed with the adjusting screw
1,500... 1,600 rpm
slowly clockwise until the idle speed begins to fall.
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