Follow up...
After much digging around I concluded that parts for these engines are getting much harder to find.
Changfa owners should gather spares while you can.
One source that I did find helpful was AliExpress (Similar to Ebay).
There were several online stores there which carry Changfa style parts.
They come and go.
I saw gasket sets, pistons, sleeves, and fuel injectors from several sellers.
https://www.aliexpress.com/