Switch off the engine. The dust cup should be emptied when 2/3 full. Frequency of dust cup service varies with the dust severity.
On dust cups with a Vacuator Valve, dust cup service is minimal. Just check the Vacuator Valve to see that it is not inverted, damaged or plugged. If it is damaged or missing, replace it immediately. Visually inspect gasket between dust cup and lower body — if worn or damaged, replace.
Tip: Save Service Time — Install Dust Dumpa on Vertical STG air cleaners!