Husqvarna HH 389MPC Operator's Manual page 12

2. Remove the sediment cup (B) and the O-ring (C).
A
3. Clean the sediment cup and the O-ring in solvent that
is not flammable.
4. Let the sediment cup and the O-ring dry fully.
5. Put the O-ring in the fuel valve and install the sediment
cup. Tighten the sediment cup fully.
6. Move the fuel valve to the ON position.
7. Examine the sediment cup for leaks. Replace the O-
ring if there is leakage.
To examine and replace the spark plug
CAUTION: Do not try to start the engine if the
spark plug or ignition cable is removed.
1. Remove the spark plug cap and clean around the
spark plug.
2. Remove the spark plug with a spark plug wrench.
3. Examine the spark plug. Replace it if the electrodes
are burned or if the insulation has cracks or damages.
If the spark plug is not damaged, clean it with a steel
brush.
4. Measure the electrode gap and make sure that it is
correct. Refer to .
a) If it is necessary, bend the side electrode to adjust
the electrode gap.
5. Install the spark plug by hand until it touches the spark
plug seat.
6. Tighten the spark plug with the spark plug wrench.
a) Tighten a used spark plug ⅛–¼ of a turn more,
and a new spark plug ½ turn more.
12
C
B
CAUTION: Spark plugs that are not
tightened correctly can cause damage to
the engine.
7. Install the spark plug cap.
To adjust the idle speed
1. Start the engine outdoors and let it become warm.
2. Move the throttle control to the low speed position.
3. Use a tachometer to do a check of the idle speed.
Refer to for correct idle speed.
4. Turn the idle speed screw (A) clockwise to adjust the
idle speed.
To do a check of the spark arrestor screen
WARNING: In some areas and conditions, you
must use a spark arrestor screen to prevent the
risk of fire. Obey local regulations.
1. Remove the 3 screws from the exhaust deflector and
remove the exhaust deflector.
2. Remove the 4 screws (A) from the muffler cover (B)
and remove the muffler cover.
B
A
A
C
D
1537 - 003 - 18.11.2022