Carburetor - Idle; Carburetor - Adjusting The Idle Speed - Husqvarna 125 TC EU Owner's Manual

15 TUNING THE ENGINE
15.3

Carburetor - idle

15.4

Carburetor - adjusting the idle speed

The idle setting of the carburetor has a big influence on the starting behavior, stable
idling and the response to throttle opening. This means that an engine with a correctly
set idle speed is easier to start than if the idle is set wrongly.
Info
The carburetor and its components are subject to increased wear caused by
engine vibration. Wear can result in malfunctioning.
The factory setting for the carburetor is set for the following values.
(125 TC EU)
L01806-11
Elevation above sea level
Ambient temperature
Super unleaded (98 octane) mixed with 2-stroke engine oil (1:40) (
(250 TC EU)
Elevation above sea level
Ambient temperature
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 air 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, or the float level is too high or the float needle valve is leaky.
500282-01
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 the engine stutters when accelerating with a partially open throttle slide, the jet needle
must be lowered by one notch. If the engine knocks when accelerating at the full power
rpm range, the jet needle must be raised. If the above events occur on idle or just above
it, the idle system must be set to a leaner setting if the engine is stuttering or to a richer
setting if the engine is 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
position.
Guideline
Idle air adjusting screw (125 TC EU)
Open
Idle air adjusting screw (250 TC EU)
Open
–
Run the engine until warm.
L01806-11
Guideline
Warm-up time
500 m (1,640 ft)
20 °C (68 °F)
500 m (1,640 ft)
20 °C (68 °F)
2 .
x
2
all the way and turn it to the specified basic
p. 101)
p. 101)
1
.
2
.
2 turns
2 turns
≥ 5 min
76
1