Carburetor Adjustment; Idling Range – A, Adjusting The Idle Speed; Part-Throttle Range – C; Full Throttle Range – D - KTM 85 SX 2004 Repair Manual

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).
Mixing ratio 2-stroke motor oil : super fuel 1:40
Basic information of changing 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 to 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 THEIR USE WILL VOID YOUR WARRANTY
– O - 2-
NLY USE HIGH GRADE STROKE ENGINE OIL OF KNOWN BRANDS
– N -
OT ENOUGH OIL OR LOW
.
FOUL THE SPARK PLUG
– I
N THE CASE OF A LEANER ADJUSTMENT OF THE CARBURETOR PROCEED CAUTIOUSLY
AVOID 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, the 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 1000 hours of using.
ROZ 95
MIXED WITH HIGH
.
GRADE OIL CAN CAUSE EROSION OF THE PISTON
.
1
2
main jet
jet needle
jet needle
idling jet
throttle valve
idling jet
choose leaner carburetor adjustment
choose richer carburetor adjustment
WARNING
- -
GRADE TWO STROKE ENGINE OIL
( . . M C P
E G OTOREX ROSS OWER
. I
F YOU USE TOO MUCH OIL
. A
LWAYS REDUCE THE JET SIZE IN STEPS OF ONE NUMBER TO
Idling range – A, Adjusting the idle speed
Operation with closed throttle valve. This range is influenced by the
position of the air control screw
make adjustments when the engine is hot.
To this end, slightly increase the idling speed of the engine by means of
the idle adjusting 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 idle adjusting screw.
Opening up – B
Engine behavior when the throttle opens. The idle jet and the shape of
the throttle valve influences this range. If, despite good idling-speed and
part-throttle setting, the engine sputters and smokes when the throttle is
fully opened and develops its full power not smoothly but suddenly at
high engine speeds, the mixture to the carburetor will be too rich, the
fuel level too high or the float needle is leaking.
Part-throttle range – C
Operation with partly open throttle valve. This range is only influenced
by the jet needle (shape and position). The optimum part-throttle setting
is controlled by the idling setting in the lower range and by the main jet
in the upper range. If the engine runs on a four-stroke cycle or with
reduced power when it is accelerated with the throttle partly open, the
jet needle must be lowered by one notch. If the engine pings, especially
when accelerating under full power at maximum engine revs, the jet
needle should be raised.
If these faults should occur at the lower end of the part throttle range at
a four-stroke running, make the idling range leaner; if the engine pings,
adjust the idling range richer.
Full throttle range – D
Operation with the throttle fully open (flat out). This range is influenced
by the main jet and the jet needle. If the porcelain of the new spark plug
is found to have a very bright or white coating or if the engine rings,
after a short distance of riding flat out, a larger main jet is required. If
the porcelain is dark brown or black with soot the main jet must be
replaced by a smaller one.
. O
THER TYPES OF GASOLINE CAN CAUSE ENGINE
2T).
,
THE ENGINE CAN START SMOKING AND
1
and the idle adjusting screw
2-2
2
. Only