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Repair manual KTM MINI 50 air/liquid cooled Art.-Nr. 3.206.028 -E
Carburetor adjustment
Basic information about 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 up to model 2005 1:40, as of model 2006 1:60.
Basic information about 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 choose leaner carburetor adjustment
low altitude or low temperatures choose richer carburetor adjustment
!
WARNING
!
–ONLY USE PREMIUM
-GRADE GASOLINE ROZ 95 MIXED WITH HIGH-GRADE TWO-STROKE ENGINE OIL. OTHER TYPES OF GASOLINE CAN CAUSE
ENGINE FAILURE
,
AND USE OF SAME WILL VOID YOUR WARRANTY
.
–O
NLY USE HIGH-GRADE 2-STROKE ENGINE OIL OF KNOWN BRANDS (I. E. Motorex Cross Power 2T).
–L
ESS OIL OR LOW
-GRADE OIL CAN CAUSE EXCESSIVE WEAR OF THE PISTON. USING TOO MUCH OIL, THE ENGINE CAN START SMOKING AND FOUL THE
SPARK PLUG
.
–I
N THE CASE OF A LEANER ADJUSTMENT OF THE CARBURETOR PROCEED CAUTIOUSLY
. ALWAYS REDUCE THE JET SIZE IN STEPS OF ONE NUMBER TO
AVOID 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., rich mixture). Therefore, these parts should be replaced after 1000 hours of using.
Idling range – A
Operation with closed throttle valve. This range is influenced by the
position of the mixture adjusting screw
1 and the idle adjusting screw
2. Only make adjustments when the engine is hot.
To this end, slightly decrease 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 mixture
adjusting screw (basic position of the mixture adjusting screw = open
3.5/3 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 then 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
Betrieb bei offenem Gasschieber (Vollgas). Dieser Bereich wird durch
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.