of course you should remove any and all casting flash you can reach.
I recommend the piston that came with the motor.
use cheap non synthetic oil at 36-to-1 ratio to break in for 6-8 heat cycles,...and pull hard on that motor to get the rings seated fully before the cylinder wall smooths out. just don't scream the rpms yet and go from low to high rpms at wide open throttle. hard pulling=rings pushed against cyl. walls extra firmly=even, full ring seating/sealing=good. then go full synthetic at whatever ratio the oil manufacturer recommends (they are all usually different,...(for example: opti2 wants you to run at 100-to-1,...no matter what engine you put it in.
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don't scream the rpms until the third or fourth heat cycle because lower end bearings need to seat/smooth out/shed micro shavings,...and wrist pin bearings also need to smooth out and shed micro shavings. these microscopic shavings will harmlessly adhere to the sticky insides/bottom of your crankcase,..and stay there causing zero harm. but they will be present and still mobile in your crankcase until 3 or 4 heat cycles and your case builds up a thin layer of oily residue that the micro-shavings can stick to and stay stuck to.
but while theyre being produced,..which is the first 3 or 4 times you run the motor,.... take it easy on the screaming rpms because they ARE potentially damaging until they stick to something inside your motor that doesn't move (sticky crankcase walls/floor) im splitting hairs here,...but the more damage you can prevent the better
a comparable scenario is running a new lawnmower engine for the first time,... and then dumping the oil. when you look closely at the used oil,..you WILL see fine,...glittery,..metal MICRO SHAVINGS. they come from every bearing/friction surface in the motor in the beginning.
it's just a fact of life
