I've bought all of my China Girl 66cc /80cc kits from BGF and I've had very good results with his stuff, like it has been said many many times......" these kits are a crap shoot no matter where you get them from" you can get a bad apple in just about any store and the same goes with these kits, they're all cheap china made stuff but they work pretty good most of the time with the right tweaking and tuning up after a good break in period.
If you want the best deal and quick shipping without a warranty BGF is the way to go.
If you want the best warranty of any vendor I know, you dont mind paying a bit extrs for the peace of mind and great customer service go with Thats Dax/ bicycle engine kit, bike engine, bicycle engine, bicycle motor
Duane is a great fella who always takes good care of his customers.
just depends on what someone wants.......
Best wishes on what ever you decide to do.