lean the low en and 8th of a turn, fly around a bit, then land turn off engine turn in another 8th of a turn an repeat process till you find it to be on the sweet spot, and also try not to change fuels to keep it running tuned....

heres one test to check to see if your low end is too rich..... have yur engine running at idle for about 30 seconds, then give it full throttle, and if it hesitates too much to hit high rpms its too rich on the low end.