The engines are nothing more than glorified lawn mower engines. Any general guide for another dirt bike or atv can apply. The only specifics are torque settings on the various bolts. Even then, the majority of torque values are very close to each other from bike to bike. Just be sure to remove bolts that should have grease on their shanks and grease them and nuts that should have blue or red thread locker on their bolt threads are removed and have thread locker applied to the bolt threads then reinstalled.
I have not needed to do anything with the engine yet so I only did settings you'd do during setup and maintenance of the general frame.
Templar X 250 PDF:
https://www.chinariders.net/showpost...&postcount=815
The only current deviation I personally do at the moment from the above PDF is I lowered the torque I put on the lower triple tee fork clamp bolts by 2 foot pounds and kept the upper clamp bolts as per the PDF.