I've never had a Honda 300ex apart, but I assume it's similar to a Honda 300 4x4... The timing chain sprocket is marked with dots. They have to align. So it doesn't matter how the motor was taken apart, you have to ensure you get the timing marks lined up and the cam put in proper. I can't tell you off the top of my head, as I always refer to my service manual.
I suggest you download a manual!!!!!
I suggest you download a manual!!!!!