Looking for some ideas here. My GX31 worked very well on the stand. Although it was a little lean on the top end with the stock carb. However once I mounted it up on the plane and inverted it, the engine would quit when going past 3/4 throttle. So I got a WYK-16 from BCMA,,thought that would cure it but I have the same problem. Engine runs great up to about 3/4 then it falls flat on its face. I hung a WT 11mm carb on it and was able to twist the hi needle out about 1/2 a turn and bang ,,full power. But I figure I''ll loose the pump with that carb on this engine..Question is can the WYK-16 be richened up,,short of drilling the jet??? and what the heck does that black press down button do on the side of the carb??