It's a case of going through the parts manual book or online, e.g. CMS
https://www.cmsnl.com/honda-nsr250_model49801/

Seals
Gear change
Kick start
Water pump (if required)
Power valve (if replating cylinders)

Gaskets
Water pump cover
Clutch cover
Lower cylinder
Cylinder head
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Why do things simply when you can complicate them