Hi ! My name is Jack I am from Toronto Canada Long time motorized bicycle fanatic used to build and ride them when I was a kid with so called "D6" Russian bicycle motor which so popular Chinese motor was copied from however Russian engine had through crankshaft induction and China simplified it by converting whole thing to piston ported induction.We also had cast iron sleve and 45cc displcement the rest of the motor is absolutely the same. Here I built two bikes.The first one was more or less stock with minor engine upgrades,the second one I went more dramatic and designed and build my own cyclinder,cylinder head,changed piston, put 18mm "Mikuni" ,build tuned expansion chamber,chain tensioner, gas tank and some other things. All in all I've got very decent result ,bicikletta running scary fast and I have huge fun riding it(more than my 750cc sport bike) Yet I stay with 50cc.This displacement has huge potential and I belive if you want somethig bigger won't you just by motorcycle? If sombody is interested in sharing this passion please contact me with no hesitation Regards. Jack.