RE: Whoa! 50CC for $220?
Depends an awful lot on who made the cranks, cases, pistons, and cylinders. Want to royally screw up a two stroke? Just cast a cylinder with lousy porting. You will spend a lot more, waaay more, than the original engine cost in replacement cylinders while you play trail and error with the porting. Many of the aftermarket engines are made entirely by the aftermarket manufacturer and don't use off the shelf parts in these areas.