carb question

Hi everyone this is my first post although I have been on the forum for about 6 months now. I have a motorized bicycle and im in the uk. My question is im looking to upgrade my standard nt carb for my 66cc china girl. And want some advice as some people seem to say yes its a good upgrade and others say not to bother as the standard carb is good enough. My current set up is
66cc china girl done about 400 miles on it now and have ported the intake and exhaust I have a sbp expansion chamber and high performance air filter,also I have sanded the head a little to increase compression. I have opened up the transfer ports a little (didnt want ti go to mad) and I have cut a slot in the piston skirt so it clears the port at tdc. I also have a jack shaft kit . So my question is what do people recomend as far as carb upgrade goes. Should I upgrade or not and if so what do I upgrade too? . Oh ment to say I have also fitted a 68jet in the nt carb and I have no 4stroking at all

thanks in advance
steve

Lol as far as how fast I want to go on a bicycle ummm dont really know I just know I have caught the bug alot of people seem to catch after they buy one of these little engines and I just want to see how far I can take it without spending silly money on it. It jus abit of fun for me at the end of the day. Anyway back to the carb to be fair the nt carb I have does seem to be set up really well for the size of it but I am jus looking into my options really and have spent the last week or more looking around on this forum but could not really find any conclusive answers as to what people are upgrading too if at all.

Lol as far as how fast I want to go on a bicycle ummm dont really know I just know I have caught the bug alot of people seem to catch after they buy one of these little engines and I just want to see how far I can take it without spending silly money on it. It jus abit of fun for me at the end of the day. Anyway back to the carb to be fair the nt carb I have does seem to be set up really well for the size of it but I am jus looking into my options really and have spent the last week or more looking around on this forum but could not really find any conclusive answers as to what people are upgrading too if at all.

just want to see how far I can take it without spending silly money on it. It jus abit of fun for me at the end of the day. Anyway back to the carb to be fair the nt carb I have does seem to be set up really well for the size of it but I am jus looking into my options really and have spent the last week or more looking around on this forum but could not really find any conclusive answers as to what people are upgrading too if at all.

Oh poo sorry