CFMOTO

I have a BMX with a CFMOTO 500cc motor it is a automatic cant keep the clutch in it. don't want to go fast. does good on flat ground I use it for hunting when I put it in low range an start up these mts [hills] it just bogs down I have put three clutches[ band clutch] in it in four yrs.  is it a clone, if so what kind of motor.would like to put a manual shift in it or just put a different motor in it.can you tell me what the problem is, my thoughts was the clutch wasn't heavy enough to do the job