Don't try and tune to max an engine that doesn't have 10 or 15 flights on it.....the engine maybe so out of tune that you would almost have to be there to see/hear it to tune it......shutting off in the air is a sign of too lean...or fuel line/tank problem......
I'll tell you the best way to tune.....low end first....pinch the line to the carb with the engine at idle.....it should run for about 5 seconds or so before you hear a pick up in rpm (leaning out due to the line pinched) and start to die...release the line......and the engine runs as before....if it revs up too soon you're too lean and you need to richen the low end...if it runs forever then your too rich and will cause coughing and burble going to high power......once set go to the high end...go to high power and what ever you do watch that PROP.....richen first , you want lots of smoke and may even be spitting oil....lean it out and you will hear an increase in rpm...as you lean, rpm will increse until it maxes out....from there either way you go is less rpm...now richen it a 1/8 to a 1/4 turn......retard power to idle and re check the low end........once good let it set at idle for a couple of minutes...don't jam the throttle to max..but advance the the throttle firmly to max...the engine should transition smoothly to high power.....all done...
make sure there are no fuel issues.....find out the factory settings by calling tower...and tune from there.....good luck