No, Royal Enfield is not the only manufacturer to produce a diesel motorcycle, but they are one of the notable manufacturers in this category. Historically, Royal Enfield has offered a diesel variant of their motorcycles, specifically the Royal Enfield Bullet. However, it's important to note that the availability of diesel motorcycles varies by region and market.
There have been other manufacturers who have experimented with diesel motorcycles as well. Some examples include:
Hatz Classic Motorcycles: This German manufacturer has produced diesel-powered motorcycles using Hatz diesel engines.
Chang Jiang: A Chinese motorcycle manufacturer that has produced diesel motorcycles using single-cylinder and twin-cylinder engines.
Track T-800CDI: A Dutch motorcycle manufacturer that has produced diesel motorcycles utilizing a three-cylinder diesel engine.
Hayes Diversified Technologies (HDT): HDT is an American company that has developed diesel-powered military motorcycles for military applications.
It's worth mentioning that the availability and production of diesel motorcycles are relatively limited compared to traditional gasoline-powered motorcycles. This is due to various factors, including the performance characteristics of diesel engines, emission regulations, market demand, and the infrastructure for diesel fuel distribution. Gasoline remains the predominant fuel choice for motorcycles worldwide.