I'm an OS guy but always am looking for a bargain. I have a lot of engines, including OS, YS, Super Tigre, Thunder Tiger, and a couple of mongrels. So far so good with my new Magnum 91. it started slobbering rich following the directions. I couldn't get it to hold on even using the Sullivan on board glow. it finally ran and held on at about 1 1/2 turns open on the main. Break-in was OK. It ran out a couple of tanks and it seems like it will be a strong runner. It even gave me a good smokey idle. The heat being on at high trim helped. Confidence is high,will report back after the maiden and a few other flights. I bought this on sale for $130! Now that's a bargain!