I have three Evolution engines, a 40, a 61, and a 100. ALL of them have the same basic problem... the adjustments on the needles are not within the limiters that the factory put on there. Sooo... I removed them. I used the 100 on an Excelleron 90 pattern plane and finally took it off in favor of an OS 1.20 AX which is absolutely delighful after all the fuss and pain I had with the Evolution 100. But, I think that with the proper feel and enough time and patients, I could have gotten it to run much better. All symptoms you had, I had. I ended going way more lean on the low end just to get it to idle. It would run a while, I would carry it out to fly and it would die. There was not one day that I got more than two flights with that engine. It would die in the air for no reason that I could think of, but it all seemed to come down to proper setting of the low end needle valve which needs to be way more lean than factory limiters would allow, and a high end that needed to be a tad more rich than the factory would allow. It seemed to always run to lean on the high end.

Again, the OS 1.20 AX cured all that and, as far as I am concerned, is the absolutely best choice for these intermediate pattern type aircraft.

In your case, however, the OS 61 SF is a grand choice over the Evo 61. Only because of the reliability and AND the support you will not get from Horizon Hobbies with the Evo. I had one (an OS 61 SF) on a Tiger 60 and only removed it because it needed rear bearings (I bought it used). It always started and ran very well and had lots of power.

DS.