Dude, you gotta get a 70cc head too... the piston is bigger, the bore in the head needs to be bigger too.
Piston slap is something we deal with with mopeds. I have 1,000 miles on a TCCD 70cc kit with a hilarious piston slap. Brand new bottom end and crank, not much play in the wrist pin bearing, good head clearance... just the way it goes on some kits.
You could actually have the piston hitting the head right now, I would STRONGLY suggest removing that head and make sure that’s not the case on a brand new top end.
I would DEFINITELY not ride it til you know what’s going on.
Get the 70cc Low comp head for that kit. High comp is too much compression without a double base gasket or spacer. (This was the case for all the K star/ tccd puch kits i’ve dealt with)