to a certain degree those cheap PP kits all make that rattley sound, the 'treats brand' DMP and TCCD seem like they are the worst. that is like reason #3 i hate building them and haven't touched one in years.
I was just discussing with a buddy of mine whether its caused by the 1 ring piston or if its piston slap or what it is making the noise. I think its piston slap based on loose tolerances on the skirt. They are probably just made real loose tolerance to be on the safe side and some of them are worse than others.
putting a better air filter/airbox quiets them down a lot but i know people who have thousands of miles and years on treats kits that have sounded like that their whole life.
definitely gotta set things up right, chamfer and gap rings, but if the rings are snagging or something real bad like that you wont make it past the first or second start.