Husqvarna 331RB Workshop Manual page 44

Idle speed (low speed)
The engine stops at idle speed.
High speed
Unsatisfactory performance at high speed.
Increase and decrease speed
The engine does not increase speed.
44 - Troubleshooting
The stop screw for the throttle does not operate correctly.
Blocked fuel filter.
Blocked fuel hose.
Air in fuel pipes.
The needle valve is defective.
Defective heat insulation seal.
The lever arm of the needle valve is too high.
The lever arm of the needle valve does not operate correctly.
The needle valve spring is damaged.
The needle valve spring is not attached correctly.
The needle valve is worn.
Object in the needle valve groove.
Blocked fuel filter.
Blocked fuel hose.
Air in fuel pipes.
Incorrect/unsatisfactory fuel.
The needle valve is defective.
The carburetor is not attached correctly.
The lever arm of the needle valve is damaged.
The lever arm of the needle valve does not operate correctly.
The needle valve spring is damaged.
The needle valve spring is not attached correctly.
The needle valve is worn.
Object in the needle valve groove.
Blocked fuel filter.
Blocked fuel hose.
Air in fuel pipes.
The needle valve is defective.
The carburetor is not attached correctly.
The lever arm of the needle valve is damaged.
The lever arm of the needle valve is too low.
The lever arm of the needle valve does not operate correctly.
The needle valve spring is not attached correctly.
Blocked needle valve.
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