2002 cr125 problem

My friend has a 2002 cr 125 that he bought for 900. I took it for a ride to see what was wrong with it, it started up no problem but it was idiling high and everytime i hit the throttle there was no power at all in the mid to high range rpms, it was almost impossible to wheelie or even do a burnout. when you hit the throttle when it is idiling it will bog. i feel like it is something wrong with the airscrew but i dont know. maybe the carb.