KTM 125 SX 2010, Owner'S Manual

Page: 69 / 899

MAINTENANCE WORK ON CHASSIS AND ENGINE
67
(250 SX)
Altitude above sea level 500 m (1,640 ft)
Ambient temperature 20 °C (68 °F)
Super unleaded gasoline, mixed with 2-stroke engine oil (1:60) ( p. 95)
The idle speed is adjusted with adjustment screw

.
The idle mixture is adjusted with idle adjusting screw

.
0 0 0 D D
0 0 C C
0 0 B B
0 0 A A
500282-01
Idle range A
Operation with the throttle slide closed. The range is influenced by the adjustment
screw

and the idle air adjusting screw

.
Transition range B
Behavior of the engine when the throttle slide is opened. This range is influenced by
the idling jet and the shape of the throttle slide.
If the engine stutters and smokes heavily when the throttle slide is opened despite a
good idle and part-load setting, and if it achieves full power abruptly at high engine
speeds, the carburetor setting is too rich, the float level is too high or the float needle
valve is not tight.
Part-load range C
Operation with the throttle slide partially opened. This range is influenced by the jet
needle (shape and position). In the lower range, the engine tuning is influenced by the
idle setting and in the upper range by the main jet.
If the engine stutters when accelerating with the throttle slide partially opened, the jet
needle must be lowered by one step. If the engine knocks during acceleration when
it reaches full power engine speed, the jet needle must be raised. If the behavior
described above is exhibited while in idle or just above idle, the idle system must be
run leaner if there is stuttering and richer if there is knocking.
Full-load range D
Operation with the throttle slide fully opened (full throttle). This range is influenced by
the main jet and jet needle.
If the insulator of a new spark plug is very light or white after riding full throttle for a
short period, or if the engine knocks, a larger main jet needs to be used. If the insula-
tor is dark brown or sooty, a smaller main jet needs to be used.
9.100
Carburetor - adjusting the idle speed
x
B00048-11
–
Screw in idle air adjusting screw

all the way and turn it to the specified basic
position.
Guideline
Idle air adjusting screw (125 SX, 150 SX)
Open 1.5 turns
Idle air adjusting screw (250 SX)
Open 1.0 turn
–
Run the engine until warm.
Guideline
Warm-up time
≥
5 min
Danger
Danger of poisoning Exhaust gases are poisonous and inhaling them may
result in unconsciousness and/or death.
–
When running the engine, always make sure there is sufficient ventila-
tion, and do not start or run the engine in an enclosed space without an
effective exhaust extraction system.
–
Adjust the idle speed with adjusting screw

.
Guideline
Choke function deactivated
–
The choke lever is pushed in to the stop. ( p. 11)
Idle speed 1,400… 1,500 rpm
–
Turn idle air adjusting screw

slowly in a clockwise direction until the idle speed
begins to fall.
–
Note the position and turn the idle air adjusting screw slowly counterclockwise until
the idle speed falls again.