Husqvarna 129C Workshop Manual page 41

The setting of the carburettor can vary a little
depending on the humidity, temperature and air
pressure.
L = Low speed needle
H = High speed needle
T = Idle adjustment screw
• The fuel quantity in relation to the air flow
permitted by the throttle opening is adjusted by
the L and H jets. Turning the needles clockwise
gives a leaner fuel mixture (less fuel) and
turning them anticlockwise gives a richer fuel
mixture (more fuel). A leaner mixture gives
higher revs while a richer mixture gives less
revs.
• The T-screw regulates the position of the throttle
while the engine is idling. Turning the screw
clockwise gives a higher idling speed while
turning it anticlockwise gives a lower idling
speed.
Basic setting
The carburettor is set to its basic setting when test
run at the factory. The basic setting is "richer" than
the optimal setting (fast idle speed is 600–800 rpm
under the recommended max. speed) and should
be kept during the engine's first working hours.
Thereafter the carburettor should be fine tuned.
The basic setting is: H = 2
1
L = 1 / turns open.
8
Both of the high and low speed jets in the
carburettor can only be adjusted using the special
tool no. 530 03 55-60.
To carry out adjustment when replacing needles
or the entire carburettor the engine must be under
load. This is achieved by fitting a standard trimmer
with the specified length (defined by the blade on
the trimmer guard) and diameter of the trimmer
cord. Consequently, the stated speed will be much
lower than with "normal" carburettor adjustment
when the engine may run freely.
After replacing the needles or the entire carburettor
on a CARB-EPA approved engine, adjustment
must be carried out according to the instructions
below.
The combiguard or trim guard must be fitted when
adjusting the H-needle.
1
/ turns open,
2
Fig 58
Fig 59
NOTE!
If the cutting equipment rotates while
idling, the T-screw must be turned
anticlockwise until it stops rotating.
A tachometer should always be used to
find the optimal setting.
Fuel system
41
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