to me, a true 50/50 machine is one where you use all the stock motor parts, not including the induction and exhaust, and do lots of fancy work to it to get 50mph.
stock piston, stock cylinder. don't get me wrong, 50mph on a 50cc moped that you can actually ride around regularly is pretty freakin awesome.. kit or not, but i have the most respect for the peds like steve's where he took a stock puch top end, went to town on the porting, played around with different pipes and carbs and timing and everything else, until he got the thing to do 50+, and still be respectable on slower rides.
this is just my opinion, and you won't catch me hating on anyone's 50cc kit that does 50+, because i know that it takes more than slapping on a kit to go fast.
plus, it's just awesome to look at steve's moped and see what looks like a stock puch moped motor sitting there, and then to have him blast by when i'm pinned in the mid 40's.