It's rather unusual for a 2 cycle gas engine to detonate unless the coil is bad and it is firing completely wrong.

Are you sure it's detonating?

Two cycle gas engines when not loaded down will make a cackling sound and some times break into what's called four cycle if they are rich enough. This is especially evident when decelerating.

Go back and peak out the top end and then richen it slightly. Then adjust your low end for smoothest running and lowest speed. then check your transition back to high speed. If it just quits, the you have to richen up the low end some to where it will speed up without quitting.

Jim