... Gen4 bicycle engine kit , USD54.85 for 48cc and USD57.55 for 80cc , direct bottom price from the ... factory supplier ! What is new and better for the Gen4 kit: ***New one piece crank , ... , takes engine more power.***1.25mm enlarger size for the intake and exhaust , lead to more power ... Connecting Rod Needle Bearings, more firm and stronger for the rod pin!***Gen3 ISO carburator, bigger slide and jet ...