Afaik, only one cvt kit (
www.24hrfun.com/series-30-cvt-belt-drive-kit-fits-phatmoto-79cc/ ) has the potential ability to achieve good top speeds with the *stock* lifan, as OP asked about. And it's been out of stock since shortly after its introduction. The common cvt kits, being rated for no less than 3hp, cannot get into the 'overdrive' range due the low horsepower of the lifan (2.5hp irl).