My articat will rev.up in natural, but when i put it in gear and go down the road it has no power can anyone tell me why this is

 

It can be many things, from a plugged main jet, bad spark plug or if you used non motorcycle type oil. Any ATV with a "wet clutch" can only use oils with no "friction modifier". If that is the case, you might be able to save the wet clutch by draining all the oil out and re filling with either Arctic Cat oil or in lieu thereof, try Shell Rotella T6 5w40. If it suddenly runs better, I would drain it after a few hours and refill with more T6.