ORIGINAL: desertpig
Awesome powerplant. Sounds to me like you may have overheated it or leaned it out. Richen the high end slightly (i.e. tune for max and then back off 200-300 RPM. Also , these engines LOVE a very lean low needle setting. They will get muddy and run too rich at midrange if the low needle is too rich.
DP
DP hit the nail on the head when he said the DA50 loves a very lean low needle. They will get VERY muddy at midrange if it's too rich on the low. I've found the best way to get the low "just right" is to keep leaning the low a little each flight until one time it actually sags while flying at 3000-4000 rpm range. Land, and open the low 1/16th turn. Now you got it. One more thing I'll throw in here. I've been running Mobil MX2T at 32:1 and just never could get my needles perfect. ie. no 4-stroking. I mixed a batch at 40:1, tweaked the low a bit, and it's never been better.....Flame suit on Dick and Ralph.
