Husqvarna 525BX Workshop Manual page 43

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 and should be kept during
the engine's first working hours. Thereafter the
carburettor should be fine tuned. The basic setting
depends on the carburettor version.
The default setting for old carburettors are:
H = 3 3/4 turns open
L = 3 3/8 turns open
The default settings for new carburettors* are:
H = 1 1/8 turns open
L = 3 3/8 turns open
* New carburettors:
• 525BX EMEA APAC (967 28 42-01):
produced after serial no SN 20171703003
and from 20171702691 to 20171702890
• 525BX US/CA (967 28 42-02):
produced after serial no SN 20172602897
• 525BX China (967 28 42-03):
produced after serial no SN 20172600101
The following conditions apply to all carburettor
settings in order to achieve the correct result:
• Defect-free spark plug with correct electrode
gap.
• Defect-free air filter. Clean and correctly fitted.
• There should be no leaks between the cylinder
and the distance piece and the carburettor and
the insulator. Check the screws are tight.
• The fuel filter should be clean.
•
The exhaust port (muffler and cylinder) should not be
completely or partially clogged.
• Correct fuel quality, minimum 89 octane.
Carefully screw in (clockwise) the L- and H-jets until
they bottom. Now unscrew (anticlockwise) the jets to the
default setting.
Use tool 530 03 55-60.
Fine adjustment
Fine adjustment of the carburettor should be
carried out after the engine has been "run-in".
The engine must also be run warm for 4 minutes.
The carburettor setting must be carried out in two
steps.
L-needle
Step 1: Turn the needle clockwise for the position
providing maximum engine speed.
Step 2: Then turn the needle anticlockwise so
that the speed drops by 600 rpm (richer setting).
H-needle
Step 1: Turn the needle anticlockwise so that the
speed drops by:
100rpm for ASPEN fuel
200rpm : for regular fuel
(richer setting)
Start the engine and check it responds quickly
at full throttle, the idle speed is to be adjusted
to 3000 rpm.
Repair instructions
43
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