Bob_nj has the correct cure for the carb fix!!! Both my twins ran the exact same way ( 3W ) and you could tweak the needles till the cows came home and it didn't make a difference any which way you turned them. I also tried venting them to the fuse but actuall had one stall and quit on landing one day so I didn't like that fix either. Since I have vented the diaphram directly over the carb with a slight taper at the end of the tube I haven't even touched the needles since the beginning of the year. The motor doesn't spit or burble in inverted flight or any other attitude for that matter, the motor runs like wild fire now,and I am completely satisfied,it was well worth the time and few penny's I spent versus the frustration and needle tweaking you can go through.