Sitting on another rider's motorcycle without their permission is generally considered inappropriate and disrespectful. Motorcycles are personal possessions, and riders may have their own preferences or rules regarding who can sit on their bike.
If you're interested in sitting on someone else's motorcycle, it's best to ask for their permission first. Respecting the owner's decision ensures that you maintain a courteous and considerate attitude towards their property.
Additionally, keep in mind that motorcycles can be delicate and easily damaged. Even if you have permission to sit on a motorcycle, it's important to exercise caution and follow any instructions given by the owner to avoid causing any accidental damage.