If you are running at 10% throttle you are not running on the main jets. No amount of leaning there is going to help. It doesn't make any difference if you change a part that is not part of the problem.
Look for a round 1/4" sheet metal cap that usually has a small round hole in the middle. It can be removed and it will expose a small adjustable needle jet. This is on the engine side of the carb and is either on the top or bottom. You might want to remove the carbs from the engine to find them.
If you have done this already then, "never mind
"