What does the top control knob do? This is a Binks M1-g spray gun. The bottom knob controls fluid but the top knob doesn't seem to make a difference on anything. I
HVLP Spray Guns - Binks
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Binks 2101-4308-2 | Conventional Spray Gun Pressure 0.070 Inch | 19ZF48 | Raptor Supplies United Kingdom