For the Thunder Tiger .61Pro, how much fuel have you run through your engine? If it is new, I think you are beating your head against a wall trying to get a good adjustment.

The running surfaces on a new engine, although they may look smooth to you, are very irregular. This causes a lot of friction which tends to make your engine stop at a low idle. For the first gallon or so, as the engine runs, these irregularities wear down and the piston and sleeve or ring and sleeve mate together very closely. Compression seal, especially in a ringed engine, will become greater. After a gallon or so, you can tweak your engine to a nice low idle.

I never worry about a good idle needle setting at first. Even if I have to have someone carry the plane out, I get some flying time on it before I waste any time tweaking.

As for buying a .61: Senior Pattern Association! Get outta here. Of course certain competitions require engine sizes, but don't they run old ST Blue Heads. Quickies run .40s, but does anyone else buy a ball bearing .40? No way, you get a .46, so why get a .61 when there are .75s and .91s available at the same weight.

A friend has a Big Stick 60 with an OS .61FX in it for a knock around plane when he isn't flying scale. The rest of the guys have Stick 40s with .46s in them. His 60 size tops out of climb while the .46 powered planes keep going. He could just as easily have a .91FX in the plane, no CG change, slightly larger prop 12-8 or 13-6 vs 12-7, if you can't clear a 14-6. The plane would take off and land the same, but have more climb and speed. If you don't like the extra speed, you throttle back.

As for the medium (.46) size engines: The .50-.53 engines are here. Ask anyone who has an OS .50 about power. Try an Irvine .53 or a Magnum .52. It's like comparing a ball bearing .40 to a .46. Cubic inches count. I see Just Engines now is offering a .56 in a .40 case and Tiger Shark also has one listed. A .56! The .61 size is being beat on from both sides. The power-to-weight ratio of a small case .56 must be something. We're talking 17 ounces vs. 25+ ounces for a .61. That's a half pound!