Carburetor Adjustment; Cleaning The Spark Arrestor (Exc Usa) - KTM 125 SX Owner's Manual

1

Carburetor adjustment *

Basic information on the original carburetor setting
The original carburetor setting was adapted for an altitude of approx. 500 meters (1600 ft.) above sea level, and the ambient
temperature of approx. 20° C (68° F), mainly for off-road use and central European premium-grade fuel (95 ROZ).
Mixing ratio (2-stroke motor oil : super fuel)
Basic information on changing the carburetor setting
Always start with the original carburetor setting (the provided factory setting is meant for break-in operation; after the break-in
period, the carburetor needs to be adjusted according to the carburetor datasheet - see appendix). Essential requirements are a clean
air filter system, air-tight exhaust system and an intact carburetor. Experience has shown that adjusting the main jet, the idling jet and
the jet needle is sufficient and that changes of other parts of the carburetor will not greatly affect engine performance.
RULE OF THUMB: high altitude or high temperatures
low altitude or low temperatures
– O -
NLY USE PREMIUM GRADE GASOLINE
GASOLINE CAN CAUSE ENGINE FAILURE
– O - 2-
NLY USE HIGH GRADE STROKE ENGINE OIL OF KNOWN BRANDS
– N -
OT ENOUGH OIL OR LOW GRADE OIL CAN CAUSE EROSION OF THE PISTON
THE SPARK PLUG AND THE EXHAUST CONTROL SYSTEM
– I
N THE CASE OF A LEANER ADJUSTMENT OF THE CARBURETOR
OVERHEATING AND PISTON SEIZURE
NOTE: If the engine does not run properly despite a changed adjustment, look for mechanical faults and check the ignition system.
Basic information on carburetor wear
As a result of engine vibrations, throttle valve, jet needle, and needle jet are subjected to increased wear. This wear may cause carbu-
retor malfunction (e.g. overly rich mixture). Therefore, these parts should be replaced after 10000 kilometers (6000 miles).

Cleaning the spark arrestor (EXC USA) *

With these models, the spark arrestor is part of the exhaust silencer. Clean it
every 4000 km (2500 miles) to guarantee proper functioning. Also clean the
spark arrestor when replacing the glassfiber yarn filling.
After assembling the silencer, remove the plug
Close the opening of the muffler with a rag and press the accelerator
approximately 20 times. The carbon deposits will be blown out through the
opening. Then turn off the engine and let the exhaust system cool down.
Grease the plug with molycote grease and mount the plug.
1:40 – 1:60
WARNING
ROZ 95 (USA = Premium RON 91)
,
AND WILL VOID YOUR WARRANTY
(
E
.
,
PROCEED CAUTIOUSLY
.
Definitions
Mixture too rich:
Too much fuel in proportion to air.
2
Mixture too lean:
1
Not enough fuel in proportion to air.
Idling range
Operation with closed throttle valve. This range is influenced by the posi-
tion of the air control screw
adjustments when the engine is hot.
To this end, slightly increase the idling speed of the engine by means of the
air control screw. Turning it clockwise produces a higher idling speed and
turning the screw counterclockwise produces a lower idling speed. Create a
round and stable engine speed using the air control screw (basic position of
the air control screw = open by 1.5 turns). Then adjust to the normal idling
speed by means of the air control screw.
(depends on oil quality)
choose leaner carburetor adjustment
choose richer carburetor adjustment
-
MIXED WITH HIGH GRADE TWO
.
. . M C P 2T).
G OTOREX ROSS OWER
.
IF YOU USE TOO MUCH OIL THE ENGINE CAN START SMOKING AND FOUL
. A
LWAYS REDUCE THE JET SIZE IN STEPS OF ONE NUMBER TO AVOID
A
2
1 and start the motorcycle.
- . O
STROKE ENGINE OIL THER TYPES OF
3
and the air control screw
41
. Only make