TUNING THE ENGINE
Carburetor - adjusting the idle speed
The idle setting of the carburetor has a big influence on the starting behavior, on sta-
ble idling, and on the vehicle response when the throttle is opened. This means that an
engine with a correctly set idle speed is easier to start than if the idle is set wrongly.
The carburetor and its components are subject to greater wear due to engine
vibrations. Wear can lead to malfunctions.
The factory setting for the carburetor is set for the following values.
Altitude above sea level
Super unleaded (95 octane) mixed with 2-stroke engine oil (1:60) (
The idle speed is adjusted with adjusting screw
The idle mixture is adjusted with the idle air adjusting screw
Idle range A
Operation with the throttle slide closed. This range is influenced by adjusting screw
and the idle air adjusting screw
Transition range B
Behavior of the engine when the throttle slide is being opened. This range is influenced
by the idling jet and by the form of the throttle slide.
If the engine sputters and smokes heavily when it starts despite a good idle and part-
load setting, and if it abruptly reaches full power at a high rpm, the carburetor setting is
too rich, the float level is too high, or the float needle valve is leaky.
Part-load range C
Operation with the throttle slide partially open. This range is influenced by the jet needle
(form and position). The idle setting influences the engine tuning in the lower range, and
the main jet influences the engine tuning in the upper range.
If, when accelerating with the throttle slide partially opened, the engine only stutters while
running, the jet needle needs to be lowered by one level. If the engine knocks, espe-
cially when it reaches the full performance engine speed while accelerating, the jet nee-
dle needs to be raised. If the behavior described above occurs while idling or just above
idling, the idling system needs to be regulated to a leaner setting if the engine is stutter-
ing and to a richer setting if knocking.
Full-load range D
Operation with the throttle slide open (full throttle). This range is influenced by the main
jet and jet needle.
If the insulator of a new spark plug is very light-colored or white after a brief ride at full
throttle, or if the engine knocks, a larger main jet needs to be used. If the insulator is dark
brown or sooty, a smaller main jet needs to be used.
Screw in idle air adjusting screw
Idle air adjusting screw (TE 125)
Idle air adjusting screw (TE USA)
Idle air adjusting screw (TE AUS)
Idle air adjusting screw (TE 250 EU)
Idle air adjusting screw (TE 300 EU)
Run the engine until warm.
500 m (1,640 ft)
20 °C (68 °F)
all the way and turn it to the specified basic posi-
≥ 5 min