Husqvarna 543RBX Workshop Manual page 69

Increase and decrease speed
The engine stops when the speed is de-
creased.
The engine cannot increase speed.
1239 - 001 -
The lever arm of the needle valve is too high.
The lever arm of the needle valve does not operate correctly.
The needle valve is worn.
Object in the needle valve groove.
Defective heat insulation seal.
Troubleshooting- 69