It is technically possible to swap engines between motorcycles, but it is important to note that engine swaps can be complex and require significant modifications to the bike's frame, electrical system, and other components.
Regarding the specific scenario you mentioned, the KTM Duke/RC 390 engine and the Dominar 400 engine have different configurations and power outputs compared to the Pulsar 200NS engine. This means that fitting either of these engines into a Pulsar 200NS would likely require extensive modifications and custom fabrication work.
The differences in engine size, mounting points, exhaust systems, and wiring harnesses could pose significant challenges during the engine swap process. Additionally, the altered power output could affect the overall performance and balance of the motorcycle, potentially leading to handling issues or other complications.
It's important to consider that engine swaps may also have legal implications. Modifying a motorcycle's engine or other major components could violate local regulations, void warranties, and affect insurance coverage.
If you are interested in modifying your motorcycle, it is strongly recommended to consult with professional motorcycle mechanics or custom bike builders who have experience with engine swaps. They can provide you with accurate guidance and assess the feasibility, costs, and potential risks associated with such modifications.