Well..that's kind of the idea when you richen any motor. The rpm will decrease.

"Normal" is never a fixed setting with any motor. They're very dependent on atmospheric
conditions, and temperature plays a HUGE role with many aspects of an engine/airplanes performance.

Lean your motor for peak, and then richen the setting by 2-300 rpm. You have to do this, or....else.

Strange you got all the way to Moki 2.1's before you learned this?

'Race