Husqvarna HS 139A Workshop Manual page 40

Increase and de- Cause
crease engine speed
The engine speed The fuel filter is blocked.
cannot be increased.
The fuel hose is blocked.
There is air in the fuel pipe.
There is vacuum leakage.
The vacuum pipe is blocked.
The screws on the pump cover are loose.
The pump diaphragm is defective.
The needle valve is defective.
The carburetor is not installed correctly.
The heat insulation seal is defective.
The needle valve lever is damaged.
The needle valve lever is too low.
The needle valve lever does not operate cor-
rectly.
The needle valve spring is not installed cor-
rectly.
The control diaphragm is damaged.
The needle valve is blocked.
The engine stops The pump diaphragm is defective.
when the engine
The needle valve lever is too high.
speed is decreased.
The needle valve lever does not operate cor-
rectly.
The needle valve is worn.
There is an object in the needle valve.
The engine speed Incorrect adjustment of the governor.
cannot be decreased.
Incorrect position of the throttle.
The slider of the governor is damaged.
40 - Troubleshooting
Solution
Clean the fuel filter. Replace the fuel filter if it
is necessary.
Clean the fuel hose. Replace the fuel hose if
it is necessary.
Use the air purge bulb to remove the air from
the fuel hose.
Examine the pump diaphragm and the pump
diaphragm gasket for wear and damages.
Replace defective parts. Refer to
mensions and wear limits on page 45 .
Clean the vacuum pipe.
Tighten the screws on the pump cover.
Replace the pump diaphragm.
Replace the needle valve.
Install the carburetor correctly. Refer to
move and install the carburetor HS 166A on
page 23 .
Replace the heat insulation seal.
Replace the needle valve lever.
Adjust the needle valve lever.
Examine the needle valve lever. Replace the
needle valve lever if it is necessary.
Install the needle valve spring correctly. Refer
To assemble the carburetor on page 27 .
to
Replace the control diaphragm.
Clean the needle valve.
Replace the pump diaphragm.
Adjust the needle valve lever.
Examine the needle valve lever. Replace the
needle valve lever if it is necessary.
Replace the needle valve.
Clean the needle valve.
Adjust the governor.
Adjust the position of the throttle.
Replace the governor.
1425 - 001 - 03.06.2020
Standard di-
To re-