The 620 definitely has a wet clutch- it is only the 900's and later 1000/1100cc (along with some early oddball 750's but that might have just been on the SS's?) bikes that enjoy the dry clutch symphony so any rattles probably aren't from that.
But obviously twins are a little lumpy running by their very nature especially if you have come from the world of Oriental in line fours but the fuel injected bikes should run smoother than the older carburetted models - it is probably a case of just getting to know each other
