Alan's right. I have both the OS 61 SF and the Super Tigre 75. I put he ST 75 on because I needed to change one of the main bearings on the OS so I put the ST 75 as a temp installation. About a week after I installed it, I heard a strange ringing sound while the plane was passing by. I landed and checked to see what the noise was. Well, the baffle inside the muffler came apart and was rattling around in there. I called ST and asked about it and they immediately sent me a replacement. Three flights later, the ringing came back, another bad muffler. I replaced it with a tuned pipe and that was that. But, I would quite a bit of wetness on the side of the plane, on the opposite side of the muffler. Turns out that the needle valve assembly on the carb was leaking fuel. Just enough to make a mess. The engine was strong and ran well, but these combinations of problems never happened with my OS.

I tried the Evolution 100 which was a disaster in waiting, and finally went back to OS. I now have about 9 OS engines in various sizes from 46 (three of them), a 50, a 61, 90, and three 1.20 AX's.

As Alan said, stick with OS. You can't go wrong.. you DO get what you paid for. $275 for a 1.20 AX with muffler and extension? I think it's right there in the competitive market, especially considering what you get.. power and reliability, easy starts, no complaints from me!! (I know..you are looking at the 61 but this is just an example of pricing. I got my 61 used and, after the bearing change, runs strong as ever).

DS.