LT80 Carb Jetting

[derf]

My sons LT80 is running like crap, we moved from FL to WY and its not ran right yet. I cleaned the 2 jets at the bottom of the Carb, and the carb in general. It won't run if its not choked. I also replaced the spark plug. Does anyone know if this is an altitude issue? What or where would I go to get the proper jet of it is, local Zuki dealer said only one jet available. Also could this be a reed valve issue? The other thing I've noticed is it smokes lots of 2-stroke oil, like the pump is working over time, could that be the problem or just an additional symptom of altitude? Thanks
Fred