need help wid 20.2mm carb from a 125 onto a neos 50

i gt a neos 50 fitted a delotoro 20.5mm carb from a neos only thing neos has is a pipe but i find wen started it sounds funny and does not want 2 pull away wen it does is doesnt go very fast at all and its got a 90 jet do u think it needs a down jet and wat size 2

 

looking at about 74-80 main jet and if its an auto choke it won't work as they are different voltage.