The exuast relief should be open when starting the motor, and while running at low (idle) speeds. For higher speeds, I would close it, mainly to cut down on noise. Is this what you have?
Edit: Actually, if you look at the K45’s big brother, the V45, the relief valve is controlled automatically via the magneto retard/advance lever. On my V-45, anything above 1/2 throttle closes the exaust relief valve.
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