One thing I think is worth doing on a China Girl is to get a half-link, cranked link, offset link, or whatever you want to call it, for the peddle chain and throw the d---ed idler as far as you can and remove the necessary links from the drive chain. BIG improvement. Also a trip to the lawnmower shop will supply a decent shutoff for the tank as well as a good filter. I always mount the coil under the tank out of the weather.
Also on most of the other type bikes I have built, I machine an ally drum the I.D. of the O.D. of the brake drum and mill 4 places to tap to insert 10 X 32 Allen heads in and then cut the drum in half laterally. Then 3 ally spacer tubes through the spokes to secure the sprocket to using 5/16" flathead Allens countersunk in the sprocket. # 41 chain works great although just used peddle chain on one OK. If I can raise $50 I am tempted to get a rope starter/centrifugal clutch so I can stick one on a little scooter. Around here they seem to let the electric scooters go without tags etc. even though they haven't peddles so maybe I can do it too. As for the rear wheel, Worksman industrial bike wheel is about $66 and has 0.010 spokes and a heavy rim wih spoke dimples like a cycle.