Remember the bigger the kit you get the more power it is making and the shorter the life of your engine. I bought and was in the process of installing a 85cc kit when I did some more research and saw all of the problems people had with wear on their engines.It's not a bad thing to get a larger bore kit but will have more chance of breakdown sooner then with smaller kit and much sooner than stock. I ended up going with a 72cc (actually 70cc)kit.I am very happy with it. If you're still looking for something bigger I have my 85cc kit which has never been used still available and for sale.
Anyhow do some research before you just go out and buy a BBK, make sure you know what mods will have to be done that go along with it free flow filter, larger main and pilot jet, free flow exhaust etc..
Good luck and heres a link to the kit I went with and am very happy with
http://www.provoscooter.com/airsal-70cc-cylinder-139qmb-50-4t.html
