Changing the number of seats on a motorcycle needs document (2) if it is covered by the type approval and does not affect safety systems; otherwise document (1).
Inspection neededYes
Certified part neededNo
What you need to know
Number of seats as approved in the type approval and not affecting safety systems (ABS): only document (2).
Not approved, or affecting safety systems: only document (1).
Document (1): report from an approved technical service on the compliance of the modifications with the legal framework (individual approval).
Document (2): conversion certificate from an automotive professional with the chassis number, a precise description of the modifications and references to the technical reports (TÜV, Gutachten) of the parts, plus copies of those reports.
The check must happen before the vehicle goes back on the road, or at the latest before the next technical inspection and never more than 2 months after the modification.
If the change is not entered in the 'remarques' field of the registration certificate, the inspection records a major defect.
If the documents are incomplete, the vehicle must go to an approved technical service for a compliance report.