Pilot circuit (mixture) screw will fix the backfiring, or shim the jet needle 0.020" if you can. Bikes always come lean from factory to meet emissions, some have a brass plug in the way of adjusting the mixture (it can be removed).

Only recommendation I have is to keep a close eye on the welds at stress points with the off brand motorcycles, their engines hold up fine but their frames tend to crack at the welds. Nothing that can't be fixed but would make for a bad day if you didn't notice the fracture starting. I have repaired a few bikes with this issue.