dangerous act placing finger over a carb with the engine running maybe bkdavy don't like his fingers
No more dangerous than trying to adjust the high speed needle with the engine running. Approach from behind the engine. This is a good way to cut the engine, particularly when you're trying to tune it. I prefer the throttle cut switch on the transmitter, which doesn't affect the idle trim, but if you don't have that option, covering the carb works quite effectively. Once you have the engine tuned, you can go back to using the idle trim switch.
But from idle up to 3/4 throttle it is perfect. After that when I open the throttle fully I don't see any more difference.
Do you mean 3/4 throttle on your transmitter? I suspect you do. The throttle servo is probably forcing the barrel into the stops at 3/4 travel. This can normally be adjusted by the "end point" adjustment on your transmitter (if it has one). It might also be referred to as the "volume' in the transmitter manual. Adjust it until the full throttle position on the transmitter just pushes the throttle barrel against the stop. Improperly adjusting this setting could lead to premature servo failure, and unnecessary drain on your battery as the servo tries to force the control arm against the stop.
Brad