After owning and hearing alot about Evolutions,no more evolutions for this guy! Seems to me that thier primarily designed for easy starting.......and thats about it! Some guys have no problems with them,but MANY other including myself have problems with them leaning themselves out in flight causing deadstick. Flown level they work nice,but during manuevers and stuff many of them seem to have a fuel draw problem. Not to mention my evolution .61 is the worst transitioning (from idle to full throttle) I've ever seen,no matter how or who tries to tune it. I was going to try crimping the exhaust pipe to give the fuel tank more pressure,but I'm not even wasting my time on that evolution anymore. I'm swaping it out of my sukhoi for some(anything) else. I'm either selling it or putting it in a non-aerobatic plane.

O.S.'s on the other hand.........Heck,in my short career here so far,I've never really seen a bad one yet! About all of them idle perfect,transfer great and never hesitate during the hardest manuevers or throttle changes. If your going 2-stroke and can afford the extra $$$ for an O.S.......do it!!!!