What Jet size??

Well, I'm having some problems with my stock 47cc carb. Starts fine, but when I start to take the choke off it dies. Yes, it has warmed up. Pulled out the jet and nothing is clogged. Just ready to upgrade to a better carb and I found a ported 47cc stock carb but have a choice between .66, .68, .70, and .72mm jets (scooterpartsrus.com, runs $40 shipped). Other than a race pipe and hp clutch springs the bike is stock. What should I get?

start with 68...next time try a search, its all over the site