Carburetor Adjustment; Basic Information On The Original Carburetor Setting; Basic Information On A Change Of The Carburetor Setting - KTM EXC Repair Manual

2-3C

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 (ROZ 95 MOZ). Mixing
ratio 2-stroke motor oil : super fuel 1:40 – 1:60.

Basic information on a change of the carburetor setting

Always start out from the original carburetor setting. 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
,
FAILURE AND USE OF SAME WILL VOID YOUR WARRANTY
– 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
.
SPARK PLUG
– I
N THE CASE OF A LEANER ADJUSTMENT OF THE CARBURETOR PROCEED CAUTIOUSLY
OVERHEATING AND PISTON SEIZURE
NOTE: If despite a changed adjustment the engine does not run properly, 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
carburetor malfunction (e.g., overly rich mixture). Therefore, these parts should be replaced after 10000 kilometers (6000 miles).
jet needle throttle valve open
N 85 A
N 85 B
0 – 1 /
4
N 85 C
0 – 1 /
4
N 85 D
– 1 /
0
4
N 85 E
– 1 /
0
4
NOZ C
NOZ D
– 1 /
0
4
NOZ E
0 – 1 /
4
NOZ F
– 1 /
0
4
NOZ G
– 1 /
0
4
NOZ H
0 – 1 /
4
NOZ I
– 1 /
0
4
NOZ J
– 1 /
0
4
N3CG
N3CH
– 1 /
0
4
N3CW
0 – 1 /
4
WARNING
ROZ 95 -
MIXED WITH HIGH
.
.
.
Explanation - Example
effect
–
Compared to the needle N 85 A, the jet needle N 85 C is two steps leaner
in the range from the closed position of the throttle to 1/4 throttle.
– –
Otherwise, there are not differences.
– – –
– – – –
–
– –
W
– – –
TYPE
– – – –
NEEDLE CAN BE USED FOR WHICH MODEL
– – – – –
– – – – – –
– – – – – – –
–
– –
choose leaner carburetor adjustment
choose richer carburetor adjustment
-
GRADE TWO STROKE ENGINE OIL
. U ,
SING TOO MUCH OIL
. A
LWAYS REDUCE THE JET SIZE IN STEPS OF ONE NUMBER TO AVOID
N 85 C
CAUTION
!
,
HEN CHANGING THE JET NEEDLE
(N 85 ,NOZ N3). T
OR HE TECHNICAL DATASHEET TELLS YOU WHICH JET
. O
THER TYPES OF GASOLINE CAN CAUSE ENGINE
THE ENGINE CAN START SMOKING AND FOUL THE
– 1 /
0
4
MAKE SURE THAT YOU USE THE CORRECT NEEDLE
.
– –
!