Motorcycles were a two-wheeled Earth vehicle.
They are a rare collector’s item by 2258. The last gasoline powered motorcycle built in 2035.
Michael Garibaldi collected all the spare parts to build a Kawasaki motorcycle but could only find instructions in Japanese, a language he had no knowledge of. 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 assistent 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. [1]
So Lennier and Garibaldi can have a ride through Babylon 5.