Bashan Storm is a great bike. Priced about the same as a TBR7, and way better build quality (we got a lemon TBR7-sold it).
JTR 279 and JTR 269 sprockets have the same measurements.
http://www.jtsprockets.com/catalogue/part/JTR269/
http://www.jtsprockets.com/catalogue/part/JTR279/
I got a JTR 279-35 for my Storm, with a 520 chain upgrade:
https://www.chinariders.net/showthread.php?t=30749
I modified washers to fit the sprocket, but it works fine. I actually dropped the gearing by about 7% for better offroad duty.
My son has inherited the Storm, complete with Tusk DSport rear tire and Shinko 524 knobby on the front. He likes it geared down too. It is easier to ride slowly in technically challenging situations. Those tires help a lot!!
I also changed the fork oil for Motul 15W. That really improved the front end. Stopped it from bottoming out all the time!