Post pictures if possible.
You will not get a goped quality engine from a china girl kit.
The best you will get is a goped type performance with a shift kit. And engine mods, plus a tuned pipe.
Sick Bike Parts LLC - Performance parts for your motorized bicycle
Count on spending more than the china girl kit cost.
I use a gp460 with a scooterguy mount. A 5 to 1 reduction transmission feeding the sick bike parts front crank setup.
40 to one in first all the way to no more oomph left in the 460 in seventh gear.
The Chinese engines do not measure cc displacement as you or I would. An 80 cc is a 66 cc.
I recently bought a 40 cc engine that turns out to be a 24 cc.
Good price but I wont buy from them again.