It sometimes happens when I start the engine and advance to full throttle, but then I go back to idle, and if I advance again it clears up (often slowly, like it's burning excess fuel - too rich?) If it doesn't work the first time, it does by the second time I cycle the throttle. So that's why takeoff is always good and with great power. If this problem does occur, it's usually after the procedure turn or after the first turnaround. Puzzler, ain't it?

Ken