Motorcycles were a type of two-wheeled Earth vehicle.
Michael Garibaldi collected all the spare parts to build a Kawasaki Ninja motorcycle but could only find instructions in Japanese, a language of which he had no knowledge. Lennier offered to help him construct the motorcycle, as he was an expert in many languages.
Lennier reconstructs the motorcycle instead of only being of assistance to Garibaldi. So first Michael is angry about it because he wanted to do it himself. Finally he bemoans that this machine can't be used because the kind of fuel it works with is forbidden. But Lennier reveals that he has fitted the machine with a non-polluting Minbari power source so that it would actually run.