My friend has a sonic low wing which he powers with an LA 40. Although this plane is designed for (I think) a 25 engine, the LA 40 is a light and mild engine, and powers the sonic wonderfully. He used an old LA engine, and after lot of use, it finally wore out. He put in a new LA engine and we took it out to try it out. The engine flies the plane fine, except a strange problem has occured. The plane rolls fairly quickly to the right, but won't roll to the left. After he tried and tried, I also flew it, and it took horizon to horizon to make a roll to the left. We examined the ailerons, and the movement seems to be equal on both sides. We also tested for slop or weakness with our hands, and the airlerons seem to be very tight and strong. This is a complete mystery. We also looked for anything in the plane that could be restricting the movement of either aileraon rods, and found nothing. It's driving us crazy. Anyone out there ever have such a weird problem? This is a first for me, and I have been flying RC for many many years.