I notice the air box is horribly designed and more of a dirt catcher then an air box. The rubber hoses on the intake in between vibrate loose and if there loose it is sucking in dirt like no tomorrow. I put 450 miles on it and I couldn't believe how much crap was in the oil filter. So I did a relocation of the air box swapped out the rubber for silicone which seal 10 times better.
For your engine burning oil the piston walls are scored. The good news is these engines are sleeved so they can be fixed.
My brother has my old 1986 suzuki 230 quad sport and is on it's 3rd piston and sleeve.