I have one of those older OS 90 4 strokes which is new by the way and while my 1st flights were great and tuned right, my last 2 flights a day or so back wasnt. I tuned it as usual with my other 4 strokes a little on the rich side and even changed the plug. But while I got it in the air it lost power at least by half. I barely had enough power to keep her in the air. As long as I gradually gained altitude so's that just in case of a deadstick I felt better but I landed and tuned and tried it again and the same thing. SO.. I just ran it REAL rich on the ground and at full power until it ran out of fuel and kept richening it up until it ran out. I havent ran it since but what do you all think might have been the problem? I dont even have a gallon through it yet. Probly not even a half gallon. But from all my 4 strokes I have and had, I havent had this problem without it just being a high end needing adjusted. HELP!