What technical modification to a motorbike will generally void the issued operating licence?

The combination you have selected is correct because both changes to the gear ratio of the pinion and chain wheel, and any modification to the engine power, can significantly affect the performance and safety of a motorbike. According to German traffic regulations, any technical modification that alters these aspects typically requires a new operating licence or a re-evaluation of the motorcycle's compliance with safety standards.

Changes such as these can impact speed, handling, and overall safety on the road. Therefore, not only is it crucial to maintain the factory specifications for these components to ensure compliance, but it also preserves the safety of the rider and other road users.

Installing a tank bag, on the other hand, generally does not impact the operating characteristics of the motorbike in a way that would void the licence. That's why it is not part of the correct answer. Understanding these regulations helps ensure that all modifications made to a motorbike maintain road safety and compliance with traffic laws.