Well today I fired the new roto 85 up and I wasn't impressed at all in the beginning. The engine was having issues like it was too lean and when I richened it up it was running real rough, so after fooling around with the needles and nothing was really doing much I noticed I put my fuel tank on the floor of my cub so I ran in and got another tank and sat it on top of the fuselage in front of the windshield and waa-laa it ran really good, so I guess you really need to have the tank a little higher than the carb so now I'm in the middle of relocating the tank higher in the fuselage. I remember when the os120 would do that if you didn't have the tank just right.