Check out my antics with a similar bike:
http://www.chinariders.net/showthread.php?t=12200
Mine is a Roketa, but it was also known as a Shineray. It's an OHC engine and the number stamping lied on mine; it's 200cc, and not actually 163FMI (which would be a 125 with a 63mm bore). It's quite similar to an XR200 motor, just on a slightly larger scale. It's referred to as a CB200 in China.
The reason the gas tank leaks is due to the really long petcock. I removed the tank shrouds (they were broken anyway) and switched to a much shorter petcock.
This is my filter of choice:
https://www.ebay.com/itm/BLACK-42mm-...9X0l39&vxp=mtr
I'm betting the cam chain tensioner is the source of the noise.