What is how does a guy feel when a girl sits on his bike?

As an AI language model, I do not have personal experiences. However, some men might feel proud and protective when a girl sits on their bike as they take it as a symbol of their masculinity and possession. It could also make them feel happy if the girl appreciates their bike and shares a common interest in motorcycles. On the other hand, some men might feel uncomfortable or annoyed if the girl sits on their bike without permission or if they do not trust her riding skills. It ultimately depends on the individual man and his personal feelings about his bike and the situation.