Re: Many questions
Yes Theon I agree, a KDX 200 or KTM 250 carb will be way to big for a china girl engine, some use 21 or 22mm Mikuni Carb on really well built engine and maybe even a 24mm on a really radical build but a 45+ mph set up can be done with an NT carb, I know because I have an engine that isn't super built, just some port work, a Puch hi hi 70cc head, manic port matched shorty intake and a well tuned NT or NT Speed carb. On the best day I saw 48mph on this bike and I dont have an expansion chamber exhaust on it either, just a home built straight through exhaust that is short and loud.....so far I haven't found anything that works better on my bikes than it does, every expansion pipe I've had on it so far decreased my top speed by several mph, im working on another that will flow better and hopefully help with better low and midrange without sacrificing the top end.....
We I said all of this to just give a little info on what some of us do to get a good strong running engine, some of it also has to do with whether or not the engine has correct timing which can vary up to about 6 degrees from what I've seen and whether or not the crank is very untrue or the balance of the rotating assembly is good enough to allow the engine to spin up to some fairly high rpms, I've seen 9400rpm on my fastest engine according to the tach I had on it I was running 40's mph with a 36T rear sprocket this bike gps' d 45.7 on the flat and I weighed 220 at the time, I have now slimmed down to 210lbs.....lol
Anyway my best advice is to do some research here on the forum to see what the people who have been doing this awhile are doing and have done and do things one step at a time....
I dont always ride WOT, but when I do..I do my best to keep the rubber side down..Ride safely my friends!