Husqvarna 439 Operator's Manual page 25

6. Some mufflers have a special spark arrestor mesh.
Clean the spark arrestor mesh one time each week if
your product has this type of muffler.
CAUTION: If the spark arrestor mesh is
blocked the product becomes too hot and
this causes damage to the cylinder and
piston.
CAUTION: The spark arrestor mesh must
be replaced if it is damaged. Do not use a
product if the spark arrestor mesh on the
muffler is missing or defective.
Carburetor with adjustment
limitations
Note: If you do not know which carburetor type that you
have on your product, speak to your servicing dealer.
Carburetor adjustment
Because of environmental and emissions laws, your
product has adjustment limitations on the carburetor
adjuster screws. This decreases the harmful exhaust
fumes from your product. You can only turn the
adjustment screws maximum ½ turn.
Basic adjustments and run-in
The basic carburetor adjustments are done at the
factory. For the recommended idle speed, refer to
Technical data on page 34 .
823 - 002 - 08.11.2018
To adjust the low speed needle (L)
• Turn the low speed needle clockwise until stop.
Note: If the product has a bad acceleration capacity
or if the idle speed is not correct, turn the low speed
needle counterclockwise. Turn the low speed needle
until the acceleration capacity and idle speed is
correct.
To adjust the idle speed screw (T)
1. Start the product.
2. Turn the idle speed screw clockwise until the saw
chain starts to rotate.
3. Turn the idle speed screw counterclockwise until the
saw chain stops.
Note: The idle speed is correctly adjusted when the
engine runs correctly in all positions. The idle speed
must also be safely below the speed at which the saw
chain starts to rotate.
To adjust the high speed needle (H)
The engine is adjusted at the factory to operate at sea
level. At higher altitudes, in different weather or different
temperatures it can be necessary to adjust the high
speed needle.
• Turn the high speed needle to make adjustments.
1/2
To examine if the carburetor is
correctly adjusted
1/2
• Make sure that the product has the correct
acceleration capacity.
• Make sure that the product 4-cycles a little at full
throttle.
• Make sure that the saw chain does not rotate at idle
speed.
CAUTION: Do not operate the product at too
high speed during the first 10 hours of
operation.
CAUTION: If the saw chain rotates at idle
speed, turn the idle speed screw
counterclockwise until the saw chain stops.
WARNING: If the saw chain does not stop
when you turn the idle speed screw, speak
to your servicing dealer. Do not use the
product until it is correctly adjusted.
CAUTION: Do not turn the high speed
needle screw across the adjustment
limitation stop. This can cause damage
to the piston and the cylinder.
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