Thanks for the reply, I think I will just remove the spark plug if it,s put in and bring the piston to bottom dead center so the exhaust port is open, shine a light in and use a mirror to see inside, if it looks OK then blow some air though to make sure.
bring the piston to top center and look in the bottom if possible, if OK, then re-torque the cylinder head and put the engine on the bike.
Maybe new cylinder head nuts and waffle washers that I have seen on meany small motors to keep head nuts tight, just have to look and see what they are.
I think caution is good, but to over do it is unnecessary with a new motor, unless you are setting it up for racing and such.
I do have the knowledge and skill to it, over 25 years as a mechanic and 5 years as a machinist.
But as above I am not interested in rebuilding a new motor.
Thanks to all that responded to my thread.