Husqvarna 531RS Workshop Manual page 59

Poor performance Fuel filter blocked
at high speed The fuel hose blocked
Air in fuel ducts
Incorrect/poor fuel
Vacuum pulse leakage
Vacuum pulse duct blocked
Loose screw(s) on the pump
cover
Faulty pump diaphragm
The needle valve is faulty
Carburettor is not fitted correctly
Needle valve's lever arm is
damaged
Needle valve's lever arm does
not work correctly
Needle valve's spring is de-
formed
The needle valve spring is not
fitted correctly
Control diaphragm is damaged
The control diaphragm has a
faulty seal
Needle valve is worn
Foreign object in the needle
valve guide
Acceleration and retardation
Engine does not ac- Fuel filter blocked
celerate The fuel hose blocked
Air in fuel ducts
Vacuum pulse leakage
Vacuum pulse duct blocked
Loose screw(s) on the pump
cover
Faulty pump diaphragm
The needle valve is faulty
Carburettor is not fitted cor-
rectly
Needle valve's lever arm is
damaged
Needle valve's lever arm is too
low
Needle valve's lever arm does
not work correctly
The needle valve spring is not
fitted correctly
Control diaphragm is damaged
Needle valve jams
The engine stops Faulty pump diaphragm
when decelerating Needle valve's lever arm too
high
Needle valve's lever arm does
not work correctly
Needle valve is worn
Foreign object in the needle
valve guide
Poor acceleration Faulty heat insulation seal
capacity
Troubleshooting
English - 59